Technology|Power system technical knowledge is the most complete 80 questions

1.500kV system voltage is too high, to be handled by on-load voltage regulation, how to regulate?

A: Adjust the tap and lower it a few times to make the voltage meet the requirements. Note: If the current direction is 500kV to 220kV, the tap changer has little effect on the 500kV system voltage. If the current direction is 220kV to 500kV, the tap changer has a greater impact on the 500kV system voltage.

2. Why can't the lightning storm be close to the arrester and lightning rod?

A: Thunderstorm weather, more lightning strikes. When a lightning strikes a lightning arrester or a lightning rod, the lightning current passes through the grounding device and enters the earth. Because the grounding device has a grounding resistance, the potential will rise very high when passing the lightning current, and may cause a counterattack or stride voltage to nearby equipment or personnel. Threat to personal safety. Therefore, lightning storms cannot be placed near lightning arresters or lightning rods.

3. What is internal overvoltage? What is atmospheric overvoltage? What is the hazard to the equipment?

Answer: The internal overvoltage is an overvoltage that is harmful to the system caused by sudden changes in the state of the power system due to improper operation or accidents or grid parameters. Atmospheric overvoltage is also called external overvoltage, which is caused by direct lightning strikes on lightning strikes caused by lightning strikes or lightning strikes on the equipment. Internal overvoltage and atmospheric overvoltage are high, which may cause flashover of weak points of insulation, causing insulation damage or even burning of electrical equipment.

4. What is the grounding resistance of the substation grounding grid?

Answer: The grounding resistance of the high current grounding system should meet R≤2000/IΩ. When I>4000A, R≤0.5Ω can be taken. When the small current grounding system is used for equipment below 1000V, the grounding resistance should meet R≤125/IΩ. When used for equipment above 1000V, the grounding resistance R≤250/IΩ resistance should not exceed 10 ohms under any circumstances.

5. What should be the grounding resistance of the lightning rod?

Answer: The grounding resistance of the independent lightning rod is generally not more than 10 ohms. The lightning rod installed on the frame has a concentrated grounding resistance of not more than 10 ohms.

6. What is the role of the isolating switch?

Answer: 1. Obvious disconnection point; 2. Cut off small current; 3. Change the operation mode.

7. The duties of the work ticket licensor?

Answer: 1. Responsible for reviewing whether the safety measures listed in the work ticket are correct and complete, whether it meets the site conditions; 2. Whether the safety measures arranged at the work site are perfect; 3. Responsible for checking the risk of sudden call failure of the power outage equipment; 4. Even if there is a small doubt, the contents listed in the list must be clearly inquired to the issuer of the work ticket and, if necessary, supplemented in detail.

8. What are the organizational measures to ensure safety?

Answer: 1. Work ticket system; 2. Work permit system; 3. Work guardianship system; 4. Work interruption, transfer and termination system.

9. Which jobs need to fill in the first job?

Answer: 1. All work on high-voltage equipment requires all power outages or partial power outages; 2. On the circuit of secondary wiring and lighting in high-voltage room, it is necessary to power off the high-voltage equipment or take safety measures.

10. Which jobs need to fill out the second work ticket?

Answer: 1. Live working and working on the outer casing of the charged equipment; 2. Control panel and low voltage switchboard. Distribution box. Work on the mains line; 3. Work on the secondary loop circuit, no need to power off the high voltage equipment 4. The generator in rotation. The excitation circuit of the synchronous camera or the rotor resistance circuit of the high voltage motor; 5. The non-duty duty officer uses the insulation rod and the voltage transformer to phase the phase or the clamp current meter to measure the high voltage circuit. Current.

11. What should the work ticket licensor do after completing the site safety measures?

Answer: 1. The person in charge of the work will go to the site to check the safety measures again, and touch the test to prove that the maintenance equipment has no voltage; 2. Indicate the position and precautions of the live equipment for the person in charge of the work; 3. Responsible for the work People sign each on the work ticket.

12. What should I pay attention to when the work ticket is closed for acceptance?

A: The person in charge of the work records the repaired project, the problems found, the test results and the existing problems, and checks the equipment status (moving wiring, pressure plate, etc.) with the person in charge of the work, whether there are any remaining items, whether the site is clean, etc. Then, fill in the work end time on the work ticket, and sign the work ticket by both parties.

13. What are the technical measures to ensure safety?

Answer: 1. Power outage; 2. Power inspection; 3. Installation of grounding wire; 4. Hanging signboard and installation of fence.

14. What are the procedures for the change of the person in charge of the work ticket?

A: When the person in charge of the work needs to be changed, the work issuer should record the change on the work ticket.

15. How many of these signs are used for each purpose?

Answer: There are six kinds of signboards: 1. On the operation handles of the switch and the knife that can be sent to the work place after being closed, all the signs should be hung on the line: “No switch, no work”; 2. If there are people on the line Work, should be on the line knife and switch operation handles to hang "no lock, the line is working" sign; 3. at the construction site near the covered equipment, on the fence of the outdoor work place, on the prohibited aisle On the outdoor test frame of the commercial pressure test site and the outdoor structure, the “stop, high pressure danger!” signboard shall be hung on the beam of the working place near the live equipment; 4. The “up and down” signboard shall be hung on the iron frame and ladder above and below the staff. 5. Hanging the “Working here” signboard at the workplace; 6. Hanging on the iron frame above and below the staff on the other iron frame that may be up and down or on the ladder of equipment such as transformers in operation. “No climbing, high voltage danger!” nameplate.

16. What is the effective time of the first and second work tickets?

A: The validity time of the first and second work tickets is limited to the scheduled maintenance period.

17. What are the main references for preventing electrical misuse?

Answer: 1) Safety regulations for electric industry; 2) 25 key requirements for preventing major accidents in power production (Guodian Corporation); 3) Minutes of professional work conferences for preventing electrical misoperations in China (No. 96.49, Ministry of Electric Power); ) Regulations for the Prevention of Electrical Misoperation Devices (Energy Department No. 90.1110); 5) Minutes of the East China Power Grid Preventing Electrical Misoperation Work Review Meeting (East China Electric Power Division 96.036); 6) Several regulations for substation operation management Company enterprise standard Q/ZDL24107001-2000A); 7) Minutes of the 99-year preventive misoperation work meeting (Hangdiansheng 99.067); 8) The management system for the use of the anti-misoperation device.

18. What are the assessment requirements for the switch operation ticket?

A: The firm is in accordance with the requirements of the Guodian Huadong Company Labor Competition.

19. What are the requirements for substation equipment signs?

Answer: 1) The first, second and third equipments on the site of the substation must have standardized, complete, clear and accurate naming marks, including terminal boxes, control boxes, power boxes, etc.;

2) The names of the secondary pressure plate, terminal, small switch, small knife, button and other components must be clearly written, and strictly consistent with the code and the on-site operation procedures;

3) The control panel and protection screen of the multi-unit should have obvious dividing lines and indicate the unit name;

4) The upper part of the terminal block of each unit behind the control screen and protection screen shall indicate the unit name;

5) On the outer casing of the tripping exit relay, it shall be marked with a clear sign prohibiting the actuation;

6) The naming mark of the equipment should be installed strictly in accordance with the equipment, and there is no time limit. It is strictly forbidden to dismantle during operation. If it needs to be temporarily removed due to work such as equipment painting, it is necessary to strictly check the accuracy of the position when reinstalling.

20. How to manage the switching operation task execution process?

Answer: 1) The switching operation should be carried out in strict accordance with the requirements of the “Eight Steps Implementation Specification for Switching Operation” (Hang Diansheng 98.0234);

2) The switching operation should be strictly performed in the switching operation. For a group of commands containing multiple operation tasks, it is strictly forbidden to change the order between tasks without authorization; for an operation task, it is strictly forbidden to change the order between the operation steps on the operation ticket without authorization;

3) If there is any doubt or obstacle in operation (such as the knife cannot be operated due to mechanical defects), the operation should be stopped immediately, the dispatcher and the leader should be reported, and the reason should be found. It is strictly forbidden to modify the operation ticket and freely release the locking device;

4) If the operation is interrupted for any reason (such as returning the main control room to take the unlocking key, etc.), when resuming the operation, be sure to re-check the contents of the current operation steps, and be sure to re-check the device logo;

5) The operations mastered by the substation (such as the electrical system used) must have the duty officer to issue the operation command, and the rest are the same as the formal operation of the dispatch;

6) Each substation operation supervisory unit shall conduct a spot check on the implementation specifications of the substation's switching operation, and at least one operation task per month. The spot check is reported to the Bureau of Biotechnology of the Bureau with the monthly report.

21. In terms of anti-misoperation, what should be paid attention to after the main equipment is finished?

Answer: 1) If the maintenance unit has dismantled or affected the anti-misoperation device and its circuit during the work, the maintenance unit shall be responsible for recovery before the end of the work, and the operation unit shall be responsible for acceptance;

2) After the maintenance unit performs large and small repairs of the switch and large and small repairs of the knives, it shall ensure that the relevant auxiliary joints operate well, and the relevant anti-misoperation loops are complete, and the operating unit is responsible for acceptance;

3) New, expanded and rebuilt projects, and the anti-misoperation device shall be designed, constructed and accepted at the same time with the main equipment.

22. What is the installation rate of the anti-misoperation device?

A: 100%.

23. What should be the elimination rate of the anti-misoperation device?

A: The elimination rate should reach 100% within 30 days.

24. Can I unlock in an emergency?

A: In case of emergency (when there is a direct threat to the person, system or equipment), if the correct operation steps are correct and the current operating equipment is correct, the person in charge of the shift can agree to unlock the operation first, and then cancel the procedure afterwards.

25. Briefly describe the configuration principles of 220kV line protection.

Answer: For 220kV lines, if there are difficulties in coordinating the stability requirements or backup protection, two sets of full-line quick-action protection should be installed. Ground short-circuit backup protection can be installed with staged or inverse time zero-sequence current protection, or grounded distance protection supplemented by phased or inverse time zero sequence current protection. Phase-to-phase short-circuit backup protection should generally be equipped with phased distance protection.

26. Briefly describe the configuration principles for 500kV line protection.

A: For 500kV lines, two complete and independent full-line quick-action main protections should be installed. Ground short-circuit backup protection can be installed with phased or inverse time zero sequence current protection. Grounding distance protection can also be used, supplemented by phased or inverse time zero sequence current protection. Phase-to-phase short-circuit backup protection can be installed with staged distance protection.

27. What is “far backup”?

Answer: “Remote backup” means that when the component fails and its protection device switch refuses to operate, the adjacent component protection device on each power supply side will operate to cut the fault.

28. What is “near backup”?

A: “Near backup” uses the dual configuration to strengthen the protection of the component itself, so that it can protect the possibility of no refusal action when the fault occurs in the zone, and install the switch failure protection to start it when the switch refuses to trip. Open the high voltage switch of the busbar of the same substation, or remotely switch the opposite side switch.

29. What is the line protection and characteristics?

Answer: Line longitudinal protection is a kind of protection device that makes the switches on both sides quickly trip when the line fails. It is the main protection of the line. It takes the specific relationship of the discriminant quantity on both sides of the line as the criterion, that is, the discriminant amount is transmitted to the opposite side by the channel on both sides, and then the two sides respectively judge the fault in the area according to the relationship between the opposite side and the discriminant amount of the side. Or an out-of-zone failure.

Therefore, the discriminating amount and the passage are the main components of the longitudinal protection device.

(1) Directional high-frequency protection is to compare the fault direction seen by each end of the line to determine whether it is an internal fault or an external fault. If the fault direction seen when the internal fault of the protected line is in the positive direction, when the external fault of the protected line is faulty, one side always sees the opposite direction. Its characteristics are:

a) require positive discrimination of the starting element to have sufficient sensitivity to line end faults;

b) A dual frequency transceiver must be used.

(2) Phase difference high frequency protection is to compare the high frequency protection of the phase of the power frequency current on both sides of the protected line. When the phase of the fault current on both sides is the same, the protection is blocked, and the protection action trips when the currents on both sides are opposite in phase. Its characteristics are:

a) It can react to various symmetrical and asymmetrical faults in the full phase state, and the device is relatively simple; b) does not react to system oscillation. Protection can continue to operate during non-full phase operation and single phase reclosing;

c) is not affected by the disconnection of the voltage loop;

d) When the channel or transceiver is deactivated, the entire protection is to be taken out of service, so separate backup protection is required.

(3) The high-frequency blocking distance protection is based on the line with the directional distance protection device as the basic protection, adding corresponding signaling and receiving equipment, and configuring the longitudinal distance protection through the channel. Its characteristics are:

a) can respond to various symmetrical and asymmetrical faults sensitively and quickly;

b) the function of maintaining backup protection;

c) When the voltage secondary circuit is disconnected, the protection will be malfunctioned, and the disconnection blocking measures shall be taken to make the protection exit the operation.

30. What is the important role of longitudinal protection in the power grid?

Answer: Since the longitudinal protection can realize full-line quick-moving in the power grid, it can ensure the stability of the parallel operation of the power system, improve the transmission power, reduce the damage caused by the fault, and improve the coordination performance between the backup protection.

31. Can the channels of longitudinal protection be divided into several types?

A: It can be divided into the following types:

(1) Power line carrier longitudinal protection (referred to as high frequency protection).

(2) Microwave longitudinal protection (referred to as microwave protection).

(3) Optical fiber longitudinal protection (referred to as optical fiber protection).

(4) Guide line longitudinal protection (referred to as guide line protection).

32. What are the signals of the longitudinal protection?

A: There are three types of signals for longitudinal protection:

(1) Blocking signal. It is a signal that prevents protection from tripping. In other words, the no-blocking signal is a necessary condition for protection to trip. The protection acts on the trip only when both the local protection component action and the no-lockout signal are met.

(2) Allow signal. It is a signal that allows the protection action to trip. In other words, there is a requirement that the enable signal is a protection action for tripping. The protection acts on the trip only when both the protection of the local protection element and the permission signal are met.

(3) Trip signal. It is a signal that directly causes a trip. At this time, regardless of whether the protection element operates or not, as long as the trip signal is received, the protection acts on the trip, and the remote trip protection uses the trip signal.

33. Briefly describe the basic working principle of the direction comparison type high frequency protection.

Answer: The basic working principle of the direction comparison type high frequency protection is to compare the fault directions seen by the two sides of the line to comprehensively judge whether it is internal or external fault of the protected line. If the fault direction seen when the internal fault of the protected line is in the positive direction, when there is a fault outside the protected line, there is always an example of the reverse direction. Therefore, the direction-comparison type high-frequency protection discriminating element is a self-directed element or a current element whose operation value can distinguish between a positive and a negative direction. The so-called fault direction of the comparison line is to compare the action behavior of the specific discrimination on both sides.

34. What are the advantages and disadvantages of high frequency blocking distance protection?

A: This protection has the following advantages:

(1) It can respond to various symmetrical and asymmetrical faults sensitively and quickly.

(2) It can still maintain the role of far backup protection (when there is sensitivity).

(3) Not affected by the distributed capacitance of the line.

The disadvantages are as follows:

(1) The series compensation capacitor can make the high frequency distance protection malfunction or refuse.

(2) The voltage secondary circuit will be mis-operated when it is disconnected. The disconnection blocking measures should be taken to get the protection out of operation.

35. What issues should be paid attention to during the operation of zero-sequence current protection?

Answer: Zero sequence current protection should pay attention to the following problems during operation:

(1) When the current loop is broken, it may cause protection malfunction. This is a common weakness of generally sensitive protection and needs to be prevented during operation. In terms of the probability of disconnection, it is much less likely to break the line than the protection voltage loop. If it is necessary, it can also be prevented by the method of zero-sequence current blocking of adjacent current transformers.

(2) When the power system is in asymmetrical operation, zero-sequence current will also occur, such as asymmetric operation caused by different three-phase parameters of the transformer, two-phase operation in single-phase reclosing, three-phase reclosing and manual combination During the different period of the three-phase switch at the gate, when the switch is connected in parallel with the knives or the normal operation of the switch, the zero-sequence circulation occurs due to the inconsistent three-phase of the contact resistance of the knives or switches, and the air-dropping transformer is running. In the case of the case, unbalanced magnetizing inrush current and DC component, etc., which may occur for a long time, may cause the zero sequence current protection to start.

(3) Parallel lines with geographical proximity. When one of the lines fails, one line may cause induced zero current on the other line, causing the relay in the reverse direction side zero sequence direction to malfunction. If this is possible, the negative sequence direction relay can be used instead to prevent the above direction relay from being misjudged.

(4) Since the zero-sequence direction relay AC circuit usually has no zero-sequence current and zero-sequence voltage, the loop disconnection is not easy to be found; when the relay zero-sequence voltage transformer opens the triangle side, it is not easy to check its direction with a more intuitive simulation method. The correctness is therefore more likely to cause protection rejection and malfunction in the event of a grid failure due to a problem with the AC loop.

36. When the phase difference high frequency protection and high frequency blocking protection are used together with the single phase reclosing, why is the high frequency protection of the difference high-speed protection to be a three-hop stop signal, and the high-frequency blocking protection should be a single-hop stop signal?

Answer: On the line using single-phase reclosing, when the non-full-phase operation is performed, the phase difference high-frequency starting components may not return. At this time, if the two-side single-hop stop signal, the stop-time cannot be consistent, the stop signal is slow. One side will trip three phases after a single-phase fault trip due to a discontinuous wave that is still emitted during non-full phase operation. Therefore, the phase difference high frequency protection cannot be stopped after the single phase fault trips. After the three-phase trip, the high-frequency protection of the phase difference loses the operating power and sends a continuous wave, which will block the high-frequency protection of the opposite phase difference. Therefore, the three-hop stop signal must be implemented, so that the contralateral phase difference high-frequency protection accelerates the trip and removes the fault. In addition, when the busbar protection action, if the switch fails, the three-hop stop signal can make the opposite side high-frequency protection action and quickly cut off. The high-frequency latching protection must implement a single-hop stop signal, because the protection will return after the single-phase fault on the single-phase fault side of the line, and the high-frequency latch-up protection start-up component will not return, the transceiver will start sending a message, and the opposite side will be sent. The latching protection is blocked. Therefore, after a single-phase trip, the signal must be stopped to accelerate the tripping of the opposite side high-frequency lockout protection.

37. One line has two sets of microcomputer protection, and the line is single-phase reclosing. How should the two sets of microcomputer protection reclosing be used?

Answer: The selection switch of the two sets of microcomputer reclosing is cut in the single weight position, and only one set is connected to the closing exit. If both sets of reclosing flapping outlets are put into operation, it may cause the switch to coincide twice in a short time.

38. Which electrical quantity is usually recorded by the microcomputer fault recorder?

Answer: For 220kV and above voltage systems, microcomputer fault recorders generally need to take voltage quantities UA, UB, UC, 3U0, current quantities IA, IB, IC, 3I0; high frequency protection high frequency signal, protection action and switch Switching signal such as position.

39. What are the characteristics of transformer magnetizing inrush current?

A: The magnetizing inrush has the following characteristics:

(1) A non-periodic component containing a large component tends to bias the inrush current to one side of the time axis.

(2) Contains a large number of higher harmonic components and is dominated by the second harmonic.

(3) There is a discontinuity between the excitation inrush current waveforms.

40. What are the current methods for preventing the influence of magnetizing inrush current in differential protection?

A: The method to prevent the influence of the magnetizing inrush current is to use a differential relay with a fast saturated iron core.

What protection and its function should be installed in the 41.500kV shunt reactor?

Answer: The high voltage shunt reactor should be equipped with the following protection devices:

(1) High impedance differential protection. Protect phase and ground faults in reactor windings and bushings.

(2) Daytime protection. Protect the reactor's turn-to-turn short circuit fault.

(3) Gas protection and temperature protection. Protects various faults inside the reactor, oil level reduction and temperature rise.

(4) Overcurrent protection. Overcurrent caused by phase or ground faults in the reactor and leads.

(5) Overload protection. Protect the reactor winding from overload.

(6) Neutral point overcurrent protection. The external ground fault of the protection reactor causes a small reactance overcurrent at the neutral point.

(7) Neutral point small reactance gas protection and temperature protection. Protects various faults within the small reactance, oil level reduction and temperature rise.

42. Describe the characteristics of medium impedance type fast bus protection.

Answer: The fast busbar protection is a medium-impedance bus differential protection with braking. The selected component is a medium-impedance current differential relay with proportional braking characteristics, which solves the busbar differential protection caused by the current transformer saturation. Misoperation in the event of an out-of-zone fault. The protection device is based on the measurement and comparison of the instantaneous value of the current. When the busbar is internally faulty, the starting component and the selection component of the protection device can operate before the current transformer is saturated, so the action speed is fast. Medium impedance type fast bus protection device features:

(1) The double busbars run in parallel, one busbar fails, and the protection device is highly selective under any circumstances.

(2) The double busbars run in parallel, and the two busbars are successively faulty, and the protection device can successively jump off all the connecting components on the two busbars.

(3) Internal fault of the busbar, the whole set of action time of the protection device is not more than 10ms.

(4) The double busbars operate normally and the protection device operates reliably.

(5) The internal bus has an internal fault during the double busbar switching operation; if two sets of knives cross the two busbars at the same time, the busbar fails, and the protection device can quickly remove all the connecting components on the two busbars, if one line When the two sets of knives are not connected to the two sets of busbars at the same time, the busbars are faulty and the protection device is still highly selective.

(6) External fault of the busbar, no matter whether the line current transformer is saturated or not, the protection device is reliable and does not malfunction.

(7) In the normal operation or switching operation, if the busbar protection AC current loop is disconnected, the protection device will lock the entire set of protection through the set delay, and issue an AC current loop disconnection alarm signal.

(8) In the substation with similar switch or switch trip time difference, the protection device can ensure that the busbar switch first jumps when the busbar fails.

(9) The fault between the current transformer of the bus-coupled switch and the bus-coupled switch, the busbar protection and the switch failure protection successively jump off all the connecting components of the two busbars.

(10) On the 500kV bus, the transient current transformer is used. When the double busbar connection knife has double span, the starting component can be without braking characteristics. In the 220kV busbar, in order to prevent the double busbar from being double-span, the starting component has the same ratio braking characteristics as the selected component.

43. Why should voltage blocking components be used in bus current differential protection?

Answer: In order to prevent the differential relay from malfunctioning or accidentally hitting the intermediate relay of the outlet, the busbar protection malfunctions, so the voltage blocking component is used.

44. How to implement voltage blocking components?

Answer: The voltage blocking component is realized by a low voltage relay and a zero sequence overvoltage relay connected to the secondary side of the voltage transformer on each bus bar. Three low-voltage relays react to various phase-to-phase short-circuit faults, and zero-sequence overvoltage relays react to various ground faults.

45. Why set busbar charging protection?

Answer: The bus differential protection should ensure that the faulty busbar is quickly and selectively disconnected when a group of busbars or a certain busbar is closed for charging. In order to more reliably remove the fault on the charged bus, current or zero-sequence current protection is set on the bus-coupled switch or the bus-segment switch as bus-bar charging protection.

The busbar charging protection wiring is simple and ensures high sensitivity at a fixed value. Where conditions permit, this protection can be used as a temporary protection for the new bus line with a dedicated bus.

Bus charging protection is only applied when the bus is charged. When charging is good, it should be deactivated in time.

46. ​​What is the "two votes and three systems"?

A: Two votes refer to work tickets and operation tickets;

The three systems refer to the shifting system, the inspection system, and the periodic testing and rotation of equipment.

47. What are the states of the equipment in the power system?

Answer: The equipment status of the power system is generally divided into four states: operation, hot standby, cold standby, and overhaul.

48. What are the systems for operating the power system?

Answer: The power system duty dispatchers should observe the following systems when operating:

Operation of the order ticket system, repeat order system, guardianship system, and recording and recording system.

49. What are the forms of scheduling operation instructions?

Answer: The dispatch operation instruction forms are: single instruction, item-by-item instruction, and comprehensive instruction.

50. What are the conditions for grid connection operation?

Answer: (1) The phase should be consistent. If the phase change may occur after the first ring or after repair, it must be determined that the phase on both sides of the ring is consistent.

(2) If it belongs to the electromagnetic ring network, the difference of the transformer wiring group in the ring network is zero; in special cases, the verification relay protection will not malfunction and the related loop equipment will not be loaded, allowing the transformer wiring. The difference is 30 degrees for the loop operation.

(3) The components in the ring network after the loop are not overloaded.

(4) The voltage of each busbar should not exceed the specified value.

(5) Relay protection and safety automatic devices should be adapted to the ring network operation mode.

(6) Stability meets the requirements of the regulations.

51. What are the accidents that can be reported by the accident unit without waiting for the dispatching instructions to be processed first?

Answer: When the following accidents occur, the unit of the accident can report it without waiting for the dispatching instructions to be processed first:

(1) When there is a threat to the person and equipment, take measures according to the site regulations.

(2) When all or part of the power consumption of power plants and substations is blacked out, use other power sources to restore self-use.

(3) When the frequency of the system accident is reduced, each power plant increases the output of the unit and opens the standby generator set into the system.

(4) The system frequency is as low as the frequency is reduced by load, and the low frequency de-listing device should be operated. When the device is not operating, the switch that should be cut by the device should be manually removed immediately after the confirmation is correct.

(5) Accidents and on-site procedures clearly stipulate accidents that can be handled by the dispatcher on duty.

52. When the substation with multiple power supplies is completely out of power, what basic methods should the substation adopt to restore power transmission as soon as possible?

Answer: When the substation with multiple power supply is completely out of power, the substation operation duty personnel should immediately disconnect the switch that may be connected between multiple power sources according to the regulations. If the double busbar busbar switch is not disconnected, the bus coupler switch should be opened first to prevent sudden change. The caller caused a non-synchronous closing. However, one main power line switch should be kept in operation on each bus, or the power supply line of the voltage measuring device should be checked to determine the incoming call time as early as possible.

53. What should I do when the busbar loses power due to the differential protection action?

Answer: (1) Double busbar wiring When the single busbar is running, the busbar protection action will cause the busbar to be powered off, and the duty dispatcher can choose to send the power line switch once. If not successful, switch to the alternate bus.

(2) When the double bus is running and the power is cut off due to the busbar protection action, the on-site duty personnel do not wait for the dispatching command, immediately pull the switch and send it once, and select which switch is forced to send, which is decided by the shift dispatcher.

(3) When one of the double busbars is powered off (selective cutoff of the busbar protection), after the faulty point is not found by the inspection equipment, the dispatch dispatcher should be immediately requested to send it once with the line switch. If necessary, the busbar switch can be used to send However, the bus coupler switch must have perfect charging protection (including phase and ground protection). If the forced transmission is unsuccessful, the faulty busbar blade is opened and the line is switched to the running busbar.

Note: There are two main methods for dealing with bus faults in power plants and substations. One method is to first send power to the faulty busbars. After the charging is successful, the busbars are restored immediately. Another method is to first faulty busbars. The disconnected switch is turned to the running bus, and then the faulty bus is tested. After the test is sent, the busbar is turned into the normal mode. Both methods have their own advantages and disadvantages. Each network should formulate relevant regulations according to the bus fault type and the busbar wiring and the nature of the load shedding.

54. What issues should be considered when sending power to the line?

A: These issues should be considered when sending power to the line:

(1) First, consider that there may be permanent faults and stability.

(2) Correctly select the strong transmission end of the line, generally away from the stable line factory and station bus line. If necessary, change the wiring mode and then send power strongly. Consider the factors affecting the stability of the power grid.

(3) There must be a transformer with a neutral point directly grounded on the busbar.

(4) Pay attention to the impact on the transient stability of adjacent lines when transmitting strongly. If necessary, reduce the power transmission before sending strong power.

(5) When the line trips or coincidence is unsuccessful, accompanied by obvious system oscillation, it should not be forced immediately. It is necessary to check and eliminate the oscillation before considering whether to send power strongly.

55. What are the principles for handling transformer accident trips?

A: The principle of handling transformer accident trips is:

(1) Check the relevant equipment for overload problems.

(2) If the main protection (gas, differential) action, no power supply must be sent before the cause is eliminated.

(3) If only the overcurrent protection (or low voltage overcurrent) action, check the main transformer can send power without any problem.

(4) The transformer with reclosing is unsuccessful after the trip. The equipment should be inspected before considering the power transmission.

(5) A substation with a standby transformer or a standby power supply that is automatically put into operation. When the running transformer trips, it should start with the standby transformer or the backup power supply, and then check the tripped transformer.

(6) If the transformer trips due to the fault of the line due to the line fault, the transformer can be resumed immediately after the fault line switch is disconnected.

56. What happens to the abnormality of the knife during operation?

A: The following should be handled separately:

(1) If the brake is overheated, try to reduce the load immediately.

(2) When the guillotine is severely heated, the load should be transferred by means of an appropriate switch to reverse the busbar or by using the standby switch to bypass the busbar to make it run out.

(3) If the heater blade is disabled, it may cause power failure and cause large losses. If the heat is not eliminated at this time, you can use the short-circuit method to temporarily short the blade.

(4) The insulator does not have serious discharge marks, the surface cracks off the glaze, etc., and the power can be temporarily cut off. After formal application for power outage, it will be processed.

57. What happens when the load pulls and closes the knife during operation?

Answer: (1) With the load closing knife, even if the fault is found, the knife will not be pulled open again. Because of the load pulling knife, it will cause a three-phase arc short circuit accident.

(2) When the blade is loaded with a wrong pull knife, an arc occurs when the blade just leaves the fixed contact. At this time, it should be closed immediately to eliminate the arc and avoid accidents. However, if the knives are all pulled apart, it is not allowed to close the erroneously pulled knives.

58. How to deal with the entire power outage of the substation?

Answer: When a substation full stop accident occurs and the substation and the dispatcher can maintain communication, the dispatch dispatcher orders the accident to resume power supply. After the substation is powered off at the whole station, the on-duty personnel can disconnect the high-voltage busbar busbar switch and operate to maintain a power line switch on each high-voltage busbar according to the regulations. All other power line switches are turned off.

When the substation is completely stopped and loses contact with the dispatch, the on-site operation duty personnel shall turn each power line into the bus line with the voltage transformer to detect whether the call is made. When the dispatcher determines that the substation is in the full stop state, it can separately send power to the substation with one or several power sources. After the substation finds an incoming call, it can send the load according to the regulations.

59. What are the common abnormalities and accidents of secondary equipment?

Answer: The common abnormalities and accidents of secondary equipment mainly include:

(1) The DC system is abnormal or faulty.

(2) The relay protection and safety automatic device are abnormal and faulty.

The DC positive pole grounding of the secondary system may cause protection misoperation, because the general trip coil (such as the protection outlet intermediate relay coil and the tripping coil) is connected to the negative power supply. If these circuits are grounded or the insulation is poor, it will cause Protection against malfunctions. The DC negative grounding is the same as the positive grounding. If there is another grounding in the circuit, it may cause protection and rejection (progressive expansion accident). Because the two-point grounding will short-circuit the trip or closing circuit, the relay contacts may also be burned out.

60. What protection does the AC loop disconnection mainly affect?

A: All protections connected to the AC circuit are affected, mainly include: distance protection, high frequency protection, direction high frequency protection, high frequency blocking protection, bus differential protection, transformer low impedance protection, loss of field protection, failure protection, Zero sequence protection, current quick disconnection, overcurrent protection, generator, transformer differential protection, zero sequence crossbar protection, etc.

61. In which cases should there be two cases of high frequency protection at the same time?

A: High frequency protection on both sides of the line should be immediately disabled in the following situations:

High frequency protection device failure;

Channel overhaul or failure.

62. In which cases should the line reclosing device be deactivated?

A: The relevant line reclosing device should be immediately deactivated in the following cases:

a. When the device is not working properly;

b. When the inspection and measurement conditions of the reclosing requirement cannot be met;

c. may cause non-synchronous closing;

d. When charging the line for a long time;

e. When the switch interrupting capacity is not allowed to coincide;

f. When there is a live working request on the line;

g. When the system has stable requirements;

h. When the number of switch trips is exceeded.

63. What are the specific provisions of “major accidents”?

A: The specific provisions of the "major accident" are:

(1) A personal death accident has reached 3 or more people at a time, or a death or serious injury has a death and serious injury of 10 or more.

(2) One of the following consequences is caused by a large-scale power outage.

a) The power system load reduction exceeds the following values:

Network load reduction load

10,000 MW and above 10%

5000~10000MW以下15%或1000MW

1000~5000MW以下20%或750MW

1000MW以下40%或200MW

b)中央直辖市全市减供负荷30%及以上；省会或重要城市（名单由电力主管部门确定）。

64．什么是正常运行方式、事故后运行方式和特殊运行方式？

答：（1）正常运行方式：包括检修方式和按负荷曲线及季节变化的水电大发，火电大发，最大最小负荷和最大最小开机方式下较长期出现的运行方式。

（2）事故后运行方式：电力系统事故消除后，在恢复到正常方式前所出现的短期稳定运行方式。

（3）特殊运行方式：主干线路、大联络变压器等设备检修及其对系统稳定运行影响较为严重的运行方式。

65．保证安全的组织措施是什么？

答：电气设备上工作，保证安全的组织措施为：

（1）工作票制度；

（2）工作许可制度；

（3）工作监护制度；

（4）工作间断、转移和终结制度。

66．保证安全的技术措施是什么？

答：在全部停电或部分停电的电气设备上工作，必须完成下列措施：

（1）停电；

（2）验电；

（3）装设接地线；

（4）悬挂标示牌和装设遮栏。

67．什么是“三不放过”？

答：发生事故应立即进行调查分析。调查分析事故必须实事求是，尊重科学，严肃认真，要做到事故原因不清楚不放过，事故责任者和应受教育者没有受到教育不放过，没有采取防范措施不放过。

68．在电气设备操作中发生什么情况则构成事故？

答：发生下列情况则构成事故：带负荷拉、合闸刀；带电挂接地线（合接地开关）；带接地线（接地开关）合开关（闸刀）。

69．高频闭锁式保护运行时，为什么运行人员每天要交换信号以检查高频通道？

答：我国常采用电力系统正常时高频通道无高频电流的工作方式。由于高频通道涉及两个厂站的设备，其中输电线路跨越几千米至几百千米的地区，经受着自然界气候的变化和风、霜、雨、雪、雷电的考验。高频通道上各加工设备和收发信机元件的老化和故障都会引起衰耗；高频通道上任何一个环节出问题，都会影响高频保护的正常运行。系统正常运行时，高频通道无高频电流，高频通道上的设备有问题也不易发现，因此每日由运行人员用启动按钮启动高频发信机向对侧发送高频信号，通过检测相应的电流、电压和收发信机上相应的指示灯来检查高频通道，以确保故障时保护装置的高频部分能可靠工作。

70．什么是零序保护？大电流接地系统中为什么要单独装设零序保护？

答：在大短路电流接地系统中发生接地故障后，就有零序电流、零序电压和零序功率出现，利用这些电气量构成保护接地短路的继电保护装置统称为零序保护。三相星形接线的过电流保护虽然也能保护接地短路，但其灵敏度较低，保护时限较长。采用零序保护就可克服此不足，这是因为：

a.系统正常运行和发生相间短路时，不会出现零序电流和零序电压，因此零序保护的动作电流可以整定得较小，这有利于提高其灵敏度；

bY/△接线降压变压器，△侧以后的故障不会在Y侧反映出零序电流，所以零序保护的动作时限可以不必与该种变压器以后的线路保护相配合而取较短的动作时限。

71．零序电流保护为什么设置灵敏段和不灵敏段？

答：采用三相重合闸或综合重合闸的线路，为防止在三相合闸过程中三相触头不同期或单相重合过程的非全相运行状态中又产生振荡时零序电流保护误动作，常采用两个第一段成的四段式保护。

灵敏一段是按躲过被保护线路末端单相或两相接地短路时出现的最大零序电流整定的。其动作电流小，保护范围大，但在单相故障切除后的非全相运行状态下被闭锁。这时，如其他相再发生故障，则必须等重合闸重合以后靠重合闸加速跳闸，使跳闸时间长，可能引起系统相邻线路由于保护不配而越级跳闸，故增设一套不灵敏一段保护。不灵敏一段是按射过非全相运行又产生振荡时出现的最大零序电流整定的。其动作电流大，能躲开上述非全相情况下的零序电流，两者都是瞬时动作的。

72．采用接地距离保护有什么优点？

答：接地距离保护的最大优点是瞬时段的保护范围固定，还可以比较容易获得有较短延时和足够灵敏度的第二段接地保护。特别适合于短线路一、二段保护。对短线路说来，一种可行的接地保护方式是用接地距离保护一、二段再之以完整的零序电流保护。两种保护各自配合整定，各司其责：接地距离保护用以取得本线路的瞬时保护段和有较短时限与足够灵敏度的全线第二段保护；零序电流保护则以保护高电阻故障为主要任务，保证与相邻线路的零序电流保护间有可靠的选择性。

73．什么叫距离保护？

答：距离保护是以距离测量元件为基础构成的保护装置，其动作和选择性取决于本地测量参数（阻抗、电抗、方向）与设定的被保护区段参数的比较结果，而阻抗、电抗又与输电线的长度成正比，故名距离保护。

74．距离保护的特点是什么？

答：距离保护主要用于输电线的保护，一般是三段或四段式。第一、二段带方向性，作为本线段的主保护，其中第一段保护线路的80%~90%。第二段保护余下的10%~20%并作相邻母线的后备保护。第三段带方向或不带方向，有的还没有不带方向的第四段，作本线及相邻线段的后备保护。

整套距离保护包括故障启动、故障距离测量、相应的时间逻辑回路与电压回路断线闭锁，有的还配有振荡闭锁等基本环节以及对整套保护的连续监视等装置。有的接地距离保护还配备单独的选相元件。

75．微机故障录波器在电力系统中的主要作用是什么？

答：微机故障录波器不仅能将故障时的录波数据保存在软盘中，经专用分析软件进行分析，而且可通过微机故障录波器的通信接口，将记录的故障录波数据远传至调度部门，为调度部门分析处理事故及时提供依据。其主要作用有：

（1）通过对故障录波图的分析，找出事故原因，分析继电保护装置的动作作为，对故障性质及概率进行科学的统计分析，统计分析系统振荡时有关参数。

（2）为查找故障点提供依据，并通过对已查证落实的故障点的录波，可核对系统参数的准确性，改进计算工作或修正系统计算使用参数。

（3）积累运行经验，提高运行水平，为继电保护装置动作统计评价提供依据。

76．什么是自动重合闸？

答：自动重合闸装置是将因故障跳开后的开关按需要自动投入的一种自动装置。

77．电力系统中为什么要采用自动重合闸？

答：电力系统运行经验表明，架空线路绝大多数的故障都是瞬时性的，永久性故障一般不到10%。因此，在由继电保护动作切除短路故障之后，电弧将自动熄灭，绝大多数情况下短路处的绝缘可以自动恢复。因此，自动将开关重合，不仅提高了供电的安全性和可靠性，减少了停电损失，而且还提高了电力系统的暂态稳定水平，增大了高压线路的送电容量，也可纠正由于开关或继电保护装置造成的误跳闸。所以，架空线路要采用自动重合闸装置。

78．重合闸重合于永久故障上对电力系统有什么不利影响？

答：当重合闸重合于永久性故障时，主要有以下两个方面的不利影响：

（1）使电力系统又一次受到故障的冲击；

（2）使开关的工作条件变得更加严重，因为在很短时间内，开关要连续两次切断电弧。

79．单相重合闸与三相重合闸各用哪些优缺点？

答：这两种重合闸方式的优缺点如下：

（1）使用单相重合闸时会出现非全相运行，除纵联保护需要考虑一些特殊问题外，对零序电流保护的整定和配合产生了很大影响，也使中、短线路的零序电流保护不能充分发挥作用。

（2）使用三相重合闸时，各种保护的出口回路可以直接动作于开关。使用单相重合闸时，除了本身有选相能力的保护外，所有纵联保护、相间距离保护、零序电流保护等，都必须经单相重合闸的选相元件控制，才能动作开关。

80．运行中的变压器瓦斯保护，当现场进行什么工作时，重瓦斯保护应由“跳闸”位置改为“信号”位置运行？

答：当现场在变压器不停电情况下乾地下述工作时重瓦斯保护应由“跳闸”位置改变为“信号”位置运行。

（1）进行注油和滤油时；

（2）进行呼吸器畅通工作或更换硅胶时；

（3）除采油要样和气体继电器上部放气阀放气外，在其他所有地方打开放气、放油和进油阀门时；

（4）开、闭气体继电器连接管上的阀门时；

（5）在瓦斯保护及其二次回路上进行工作时；

（6）对于充氮变压器，当油枕抽真空或补充氮气时，变压器注油、滤油、更换硅胶及处理呼吸器时，在上述工作完毕后，经1h试运行后，方可将重瓦斯投入跳闸。