JPH04325830A - Protective unit for synchronous phase modifier - Google Patents

Abstract

PURPOSE:To provide a protective unit for synchronous phase modifier which does not function erroneously during phase lag operation under low excitation and in which the synchronous phase modifier is paralleled off quickly from a power system before it enters into phase lag operation upon missing of field during interlinked operation with the power system. CONSTITUTION:The protective unit for synchronous phase modifier comprises a reactive power drop rate detector 12 detecting drop rate of reactive power being fed from a synchronous phase modifier 1 to a power system 2 and functioning upon deviation of thus detected drop rate from a predetermined value, a field current drop detector 13 which functions when the field current of the synchronous phase modifier 1 drops below a predetermined level, and an emergency stop sequence 14 for paralleling off the synchronous phase modifier l from the power system 2 upon function of the reactive power drop rate detector 12 and the field current drop detector 13.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection device for a synchronous phase modulator that detects field abnormalities in the synchronous phase modulator.

0002

2. Description of the Related Art Conventionally, detection of field loss in a synchronous phase modifier is as shown in FIG. Synchronous phase modifier 1 is main transformer 3
and is electrically connected to the power system 2 via the parallel circuit breaker 4 . The automatic voltage regulator 5 adjusts the field current of the synchronous phase modifier 1, and controls the field current via the excitation device 6 so that the voltage of the power system 2 becomes a predetermined value.

On the other hand, the terminal voltage of the synchronous phase modifier 1 is detected by an instrument transformer 7, and the terminal current is detected by an instrument current transformer 8. The terminal voltage and terminal current detected here are input to an offset Maw type field loss relay 40 to detect a field abnormality.

FIG. 4 is a diagram showing the impedance locus of the synchronous phase modifier 1 when the field is lost.

[0005] While the synchronous phase modifier 1 is operating in conjunction with the power system 2, some abnormality occurs in the automatic voltage regulator 5 or the excitation device 6, and the field winding does not flow through the field winding of the synchronous phase modifier 1. When a loss occurs, the operating trajectory of the synchronous phase modifier 1 is a circular area 22 whose diameter is the difference (absolute value) between the synchronous reactance (Xd) and half of the transient reactance (X'd) of the synchronous phase modifier 1. Go inside. This is detected by an offset Maw type field loss relay 40 provided in the secondary circuit of the instrument transformer 7 and instrument current transformer 8 connected to the main circuit of the synchronous phase modifier 1, and operates a blocking relay (not shown). protection control has been performed to disconnect the synchronous phase modifier 1 from the power system 2.

However, in such protection control of the synchronous phase modifier 1, detection is performed after the field of the synchronous phase modifier 1 is completely lost and the phase has entered the slow phase operation region. This is the detection after the function has worked in the direction of lowering the value. In other words, if field loss occurs while the synchronous phase modifier 1 is performing phase advance operation (strong excitation operation) in an attempt to raise the voltage of the power system 2, the detection of the field loss will be delayed, so the synchronous phase modifier will A slow phase operation (weak excitation operation) is performed while being connected to the power system 2. Therefore, it not only impairs the function of raising the voltage of the power system 2, but also works in the direction of lowering the voltage of the power system 2.

Furthermore, when the characteristic circle area 22 of the offset mode is widened in order to increase the detection sensitivity of the field loss relay 40, the operating point during the slow phase operation (weak excitation operation) of the synchronous phase modifier 1 is at the field loss point. There is a risk that the voltage will fall within the detection range of the relay 40, and the synchronous phase modifier 1 will be unnecessarily disconnected from the power system 2, and the voltage maintenance function of the synchronous phase modifier 1 will not be fully demonstrated.

An object of the present invention is to quickly disconnect the synchronous phase modifier 1 from the power system 2 before the synchronous phase modifier 1 enters slow-phase operation when field loss occurs while the synchronous phase modifier 1 is operating in conjunction with the power system. In addition, the present invention provides a protection device for a synchronous phase modifier that does not malfunction during slow phase operation with low excitation. [Structure of the invention]

[0009]

[Means for Solving the Problems] The present invention provides a reactive power reduction rate detector that detects the reduction rate of reactive power supplied to the power system by a synchronous phase modulator and operates when the reduction rate deviates from a predetermined value; The field current drop detector, which operates when the field current of the synchronous phase modifier is below a predetermined value, and the reactive power drop rate detector and field current drop detector, which operate, remove the synchronous phase modifier from the power system. The present invention is characterized by having an emergency stop sequence.

0010

[Effect] As a result, the synchronous phase modifier detects the rate of reduction in reactive power during operation in conjunction with the power grid, and detects two conditions: the rate of reduction in reactive power is large and the field current is smaller than the normal operating range. When the condition is satisfied, the synchronous phase modifier is disconnected from the power grid.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a single line diagram of synchronous phase modifier equipment to which the synchronous phase modifier protection device of the present invention is applied.

The synchronous phase modifier 1 is connected to a power system 2 via a main transformer 2 and a parallel circuit breaker 4, and the field current is controlled by an automatic voltage regulator 5 via an excitation device 6. That is, the system voltage of the power system 2 is
and is compared with the voltage setting value of the grid voltage setter 9 by the grid voltage comparator 10. Then, the automatic voltage regulator 5 controls the field current of the synchronous phase modifier 1 so that the deviation becomes zero.

On the other hand, the terminal voltage of the synchronous phase modifier 1 is detected by a voltage transformer 7b, the terminal current is detected by a voltage transformer 8, and the reactive power is calculated by a reactive power converter 11. The reactive power calculated here is the reactive power decrease rate detector 1
2, and when the reactive power decreases by a predetermined rate of change or more, a stop command is output to the emergency stop sequence 14.

The field current drop detector 13 issues a stop command to the emergency stop sequence 14 when the field current of the synchronous phase modifier 1 becomes less than a predetermined value, and the emergency stop sequence 14 detects the field current drop. When a stop command is output from both the circuit breaker 13 and the reactive power reduction rate detector 12, a shutdown command is issued to the parallel circuit breaker 4.

Assume now that the voltage of the power system 2 has decreased. Then, the automatic voltage regulator 5 issues a strong excitation command, which causes the synchronous phase adjuster 1 to supply phase-advanced reactive power to the power system 2. In such a state, the excitation device 6
If field loss occurs due to an abnormality, the synchronous phase modifier 1
The reactive power changes rapidly from the fast-phase region to the slow-phase region. This sudden change is detected by the reactive power drop rate detector 12, while the loss of field current is detected by the field current drop detector 13. The operating signals of the reactive power drop rate detector 12 and the field current drop detector 13 are input to an emergency stop sequence 14, which interrupts the circuit breaker 4 and switches the synchronous phase modulator 1 to the power system 2. Disassemble more quickly.

As described above, in the present invention, when the synchronous phase modifier 1 is operating in conjunction with the power system 2 as shown in FIG. 2 (condition 41), the reactive power of the synchronous phase modifier 1 is detected. A sudden drop in reactive power is detected when the reactive power reduction rate is excessive (condition 101), and an abnormality on the excitation device 6 side is detected when the field current is below the specified minimum current (condition 121). (Condition 2)
00), it is determined that field loss has occurred in the synchronous phase modifier 1 (judgment 201), and the synchronous phase modifier is immediately disconnected from the power grid (command 202), so that it functions in the direction of raising the grid voltage. Even if field loss occurs in the synchronous phase modifier 1, it is detected before it enters the slow phase operation region, eliminating problems such as lowering the system voltage.

[0017]

As described above, according to the present invention, when the synchronous phase modifier 1 is performing phase advance operation (strong excitation operation) to maintain the voltage of the power system 2, the excitation device 6, etc. Even if field loss occurs due to an abnormality, it can be detected before the synchronous phase modifier 1 enters phase-lag operation, and the synchronous phase modifier 1 can be disconnected from the power system 2 faster than the power system 2. It functions in the direction of lowering the voltage of the power grid 2 and does not have a negative effect on maintaining the grid voltage. Further, during slow phase operation under low excitation, the synchronous phase modulator 1 will not be stopped unnecessarily due to a erroneous determination that the field has been lost.

[Brief explanation of drawings]

FIG. 1 is a single-line diagram of synchronous phase modifier equipment to which the synchronous phase modifier protection device of the present invention is applied.

FIG. 2 is a protection control block diagram according to the present invention.

FIG. 3 is a single-line diagram of a conventional synchronous phase modifier.

FIG. 4 is a characteristic diagram showing the characteristics of a conventional field loss relay.

[Explanation of symbols]

1 Synchronous phase modifier 2 Power system 3 Main transformer 4 Parallel circuit breaker 5 Automatic voltage regulator 6 Excitation device 7 Instrument transformer 8 Current transformer for instruments 9 System voltage setting device 10　　　　　System voltage comparator 11 Reactive power converter 12 Reactive power reduction rate detector 13 Field current drop detector 14 Emergency stop sequence 40 Field loss relay

Claims (1)

[Claims] 1. A protection device for a synchronous phase modifier that adjusts reactive power in a power system, wherein the synchronous phase modifier detects a rate of decrease in reactive power supplied to the power system, and when the rate of decrease deviates from a predetermined value. an operative reactive power reduction rate detector;
a field current drop detector that operates when the field current of the synchronous phase modulator is below a predetermined value; and a field current drop detector that operates when the reactive power drop rate detector and the field current drop detector operate. A protection device for a synchronous phase modifier, characterized in that it is equipped with an emergency stop sequence for disconnecting from the power system.