1. Voltage transformer body fault Internal fault of the voltage transformer, the circuit wire is damped, corroded and damaged to short-circuit the secondary winding, a phase-to-ground short circuit occurs, and a short circuit is encountered. Hesitate to short-circuit point before the secondary fuse, fault point It will not be isolated automatically until the high pressure fuse melts.
2. Voltage transformer body failure method to exit the protection and automatic device that may malfunction, disconnect the secondary switch of the fault voltage transformer (or remove the secondary insurance), the three-phase or one-phase high voltage fuse of the voltage transformer has been blown, can pull Open Disconnector Isolation Fault The high-voltage fuse does not break the uninsulated fault of the high-voltage side insulation. You can open the isolation switch to isolate the fault. When you have a qualified current-limiting resistor on the high-voltage insurance, you can open the isolation switch according to the site regulations. Isolation of the fault voltage transformer in the eye; use the reverse operation to isolate the fault. Otherwise, pull off the disconnector in the uncharged condition, and then restore the power supply.
3. In the circuit of AC voltage loop broken fault voltage, common faults are one or two insurance fuses or failures and breaking. Commonly used in the secondary circuit are: fuse blowing or poor contact, poor contact of the auxiliary contact of the isolating switch, disconnection of the voltage switching circuit or poor contact, and short circuit in the circuit. These faults cause relay protection and automatic equipment to lose AC voltage, may malfunction, and the meter indication is incorrect.
(1) A circuit reports a "voltage loop broken" signal. a symbol and reason. A circuit reports a "voltage loop disconnection" signal, the alarm sounds, the marking indication of the line is reduced to zero, the protection loses AC voltage, and the disconnection blocking device does. Fault: There is no problem in the circuit and equipment of AC voltage small bus and above, and the fault should only be in the part of secondary circuit related to the line. The main reasons are: disconnection of the voltage switching circuit for protection and instrumentation, and poor contact. b Special care must be taken when dealing with the cause of this fault. Distance protection In the event of a disconnection of the AC voltage, the DC operating power supply is disconnected and when it is closed again, tripping may be triggered by mistake. There has been a distance protection when the AC voltage is disconnected, the disconnection blocking device operates, due to the DC operation insurance interrupted contact failure malfunction tripping accident. Therefore, in this case, DC operation insurance cannot be installed and removed when distance protection is not withdrawn.
(2) AC "voltage circuit disconnection", protection "DC voltage loop disconnection" approach: A check voltage switching relay (AC voltage loop 1ZJ, 2ZJ) contacts are not closed due to reasons: a. The voltage across the coil can be measured on a switching relay that corresponds to a main circuit running bus (bus-side isolation switch in the closing position). If the voltage is normal, the relay contact may not be turned on (after multiple operations), or the relay coil may be disconnected. b. The voltage is very low, and the operating power is normal, it may be the poor contact of the auxiliary contact (1QS, 2QS) of the disconnector, or the connection terminal in the circuit.
3) Check the reason why the voltage switching relay contact is closed. The AC bus voltage at the input terminal of the small bus to measure the voltage and the protection circuit is normal. If the small bus introducing terminal voltage (A630) is normal, and the AC voltage (A710) of the protection circuit is abnormal, it may be that the contact of the switching relay contact is poor, or there is a disconnection point or a bad contact in the terminal block, terminal, etc.
4) Pay attention to prevent the AC voltage loop from being short-circuited when handling, respectively as follows: a. If there is a problem with the contact of the terminal wire and the auxiliary contact, you can deal with it by yourself and open the protection relay to prevent the protection from malfunction. b. The failure to handle the win-on-schedule schedule and related superiors, withdrawal may be mishandled protection. c. In case of poor contact of the auxiliary contact of the isolation switch, the method of the Huang Yong isolation switch operating mechanism and the prevention of disconnection of the live isolation switch shall not be used, resulting in an accident.
5) The main reason for high-voltage insurance fuse.
a) Single-phase intermittent arc grounding occurs in the system. Because at this time there will be an overvoltage (2.5 to 3 times the phase voltage), the core of the voltage transformer will saturate, and the excitation current will drastically increase to make the high voltage fuse blow. It can be seen that when reporting a ground signal, there is a system ground signal that can directly doubt whether the high voltage fuse is blown.
b) Ferroresonance overvoltage. When the system is operating single-phase grounding or disconnection fault, under certain conditions, it may generate ferromagnetic resonance, but also overvoltage, excitation current is more than ten times, so that high-voltage insurance fuse.
c) Faults such as internal short-circuit grounding of the voltage transformer and serious short circuit between turns.
d) A short circuit occurs above the secondary (or secondary circuit breaker) or the secondary circuit is short circuited and the secondary fuse is not blown.
2. Voltage transformer body failure method to exit the protection and automatic device that may malfunction, disconnect the secondary switch of the fault voltage transformer (or remove the secondary insurance), the three-phase or one-phase high voltage fuse of the voltage transformer has been blown, can pull Open Disconnector Isolation Fault The high-voltage fuse does not break the uninsulated fault of the high-voltage side insulation. You can open the isolation switch to isolate the fault. When you have a qualified current-limiting resistor on the high-voltage insurance, you can open the isolation switch according to the site regulations. Isolation of the fault voltage transformer in the eye; use the reverse operation to isolate the fault. Otherwise, pull off the disconnector in the uncharged condition, and then restore the power supply.
3. In the circuit of AC voltage loop broken fault voltage, common faults are one or two insurance fuses or failures and breaking. Commonly used in the secondary circuit are: fuse blowing or poor contact, poor contact of the auxiliary contact of the isolating switch, disconnection of the voltage switching circuit or poor contact, and short circuit in the circuit. These faults cause relay protection and automatic equipment to lose AC voltage, may malfunction, and the meter indication is incorrect.
(1) A circuit reports a "voltage loop broken" signal. a symbol and reason. A circuit reports a "voltage loop disconnection" signal, the alarm sounds, the marking indication of the line is reduced to zero, the protection loses AC voltage, and the disconnection blocking device does. Fault: There is no problem in the circuit and equipment of AC voltage small bus and above, and the fault should only be in the part of secondary circuit related to the line. The main reasons are: disconnection of the voltage switching circuit for protection and instrumentation, and poor contact. b Special care must be taken when dealing with the cause of this fault. Distance protection In the event of a disconnection of the AC voltage, the DC operating power supply is disconnected and when it is closed again, tripping may be triggered by mistake. There has been a distance protection when the AC voltage is disconnected, the disconnection blocking device operates, due to the DC operation insurance interrupted contact failure malfunction tripping accident. Therefore, in this case, DC operation insurance cannot be installed and removed when distance protection is not withdrawn.
(2) AC "voltage circuit disconnection", protection "DC voltage loop disconnection" approach: A check voltage switching relay (AC voltage loop 1ZJ, 2ZJ) contacts are not closed due to reasons: a. The voltage across the coil can be measured on a switching relay that corresponds to a main circuit running bus (bus-side isolation switch in the closing position). If the voltage is normal, the relay contact may not be turned on (after multiple operations), or the relay coil may be disconnected. b. The voltage is very low, and the operating power is normal, it may be the poor contact of the auxiliary contact (1QS, 2QS) of the disconnector, or the connection terminal in the circuit.
3) Check the reason why the voltage switching relay contact is closed. The AC bus voltage at the input terminal of the small bus to measure the voltage and the protection circuit is normal. If the small bus introducing terminal voltage (A630) is normal, and the AC voltage (A710) of the protection circuit is abnormal, it may be that the contact of the switching relay contact is poor, or there is a disconnection point or a bad contact in the terminal block, terminal, etc.
4) Pay attention to prevent the AC voltage loop from being short-circuited when handling, respectively as follows: a. If there is a problem with the contact of the terminal wire and the auxiliary contact, you can deal with it by yourself and open the protection relay to prevent the protection from malfunction. b. The failure to handle the win-on-schedule schedule and related superiors, withdrawal may be mishandled protection. c. In case of poor contact of the auxiliary contact of the isolation switch, the method of the Huang Yong isolation switch operating mechanism and the prevention of disconnection of the live isolation switch shall not be used, resulting in an accident.
5) The main reason for high-voltage insurance fuse.
a) Single-phase intermittent arc grounding occurs in the system. Because at this time there will be an overvoltage (2.5 to 3 times the phase voltage), the core of the voltage transformer will saturate, and the excitation current will drastically increase to make the high voltage fuse blow. It can be seen that when reporting a ground signal, there is a system ground signal that can directly doubt whether the high voltage fuse is blown.
b) Ferroresonance overvoltage. When the system is operating single-phase grounding or disconnection fault, under certain conditions, it may generate ferromagnetic resonance, but also overvoltage, excitation current is more than ten times, so that high-voltage insurance fuse.
c) Faults such as internal short-circuit grounding of the voltage transformer and serious short circuit between turns.
d) A short circuit occurs above the secondary (or secondary circuit breaker) or the secondary circuit is short circuited and the secondary fuse is not blown.
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