JPS5854827A - Power load unbalance relay - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a means for detecting a load loss accident in a generator, and in particular, a means for detecting a load loss accident in a generator connected to a power transmission line having a large charging capacity. Regarding load unbalance relay.

Conventional power load unbalance relays employ a method that detects changes in active power or current. However, each of these had the following drawbacks.

(1) Method based on detection of effective force - responds even to simple reclosing accidents, and there is a risk of malfunction.

(2) Method of detecting changes in current - In response to a load loss accident, a charging current flows through the transmission line. Undetectable in this state.

Among the above, method (2) of detecting with direct current can be properly detected by installing a glue handle to compensate for the charging current. Conventionally, this method was adopted by installing a compensating reactor. was.

FIG. 5 shows a conventional detection method. Conventionally, the difference between the turbine output and the generator load (current value is used) is 1% or more, and the deceleration of the generator load is 3mS in K2%/
In the above, control was performed by opening the bypass valve and closing the control valve.

An object of the present invention is to provide a load unbalance relay that does not require the installation of a shunt reactor and does not cause malfunction.

The inventors investigated whether it is possible to detect a loss of load accident without installing a shunt reactor. Since then, it has become clear that if a shunt reactor is not installed, reactive power will advance in phase due to the current of line charging during a load loss accident.

For this reason, the inventors determined the generator load, which was conventionally seen in terms of current, in terms of actual active power, and learned from the fact that reactive power has become phase-advanced, thereby eliminating the need to provide a shunt reactor. devised the present invention by focusing on the ability to detect load loss accidents.

Embodiments of the present invention will be described below with reference to FIG.

FIG. 1 schematically shows a case where a generator G is connected to a system S via a power transmission line (Ll, B2).

Generator G is driven by turbine T. The turbine T is driven by receiving steam generated from the boiler N through the pipe P1, and then is driven by the steam generated from the boiler N through the pipe P2. The water is returned to the boiler N through the condenser R via P. The generator G is connected to power transmission lines IL, , B2 via a step-up transformer Tr1, and connected to the grid via a transformer Tr2. Here, B,
, B2 indicates the busbar, CB, to CB6 are the circuit breakers, and C, , C2 indicates the capacitance of the power transmission line.

The turbine output is taken in by the sensor S, and the voltage and current of the generator are taken in by the judgment part CP through the voltage transformer PT and the current transformer CT, and the signal from the judgment part CP is taken in according to the logic shown in FIG. Bypass valve BV and control valve V in FIG. 1 are operated by this.

Figure 2 shows the difference between the turbine output and the generator load from the voltage and current information, and if this difference is q6 or more and the generator load reduction rate is 3mS or more, it is invalid. The resultant force is calculated, and if this value is advanced, the bypass valve BV is opened and the control valve v is closed at the same time.

By doing this, the steam from the boiler can be passed through the vibrator P3. P, , P,.

It passes through the condenser box and returns to the boiler N, and even though there is a large difference between the active power of the generator G and the turbine output, it is possible to prevent a phenomenon in which the turbine input is applied and the generator accelerates.

Next, FIG. 3 will be explained. FIG. 3 is a diagram when an accident occurs on bus B2 at time t1 while the generator is operating with active power P1, slow phase reactive power Q, and current ■1. Due to the occurrence of the accident, the active power became zero, the reactive power became the slow phase Q2, and the current became ■2. The reactive power at this point is due to the transformer TrI and the transmission line actance, so the generator output is delayed in phase.
It increases from the value before time 1°. At time t2, circuit breaker CB2. CB, , CBo are released. Since the generator is in a state of charging the power transmission lines L1 and B2, a current 3 determined by the capacitance C, C2 flows, and reactive power Q3
becomes progressive.

At this point, the judgment unit CU detects that the generator G has been disconnected according to the logic shown in FIG. to prevent generator G from accelerating.

FIG. 4 is an example of a case where an accident occurs at point F on the power transmission line L1 in FIG. As for the generator output before the accident, as in Fig. 3, the active power is Pl, the reactive power is Ql, and the current at this time is 11. When an accident occurs at time t1, the effective mental force P1 becomes zero, and the current ■1 becomes 12'.
Reactive power Q1 changes to Q2'. When the circuit breakers CB, , CB2 are cut off at time 12', the active power P1, the reactive power Q11 and the current ■1 change, and P2/
, Q3/, I3/.

At this time, since power is being sent from the generator side to the grid side, there will be no phase advance, and the excess of the hypochondriacal output over the input is adjusted by a governor (not shown). Therefore, rapid control by a power imbalance relay is not necessary.

As described above, regardless of whether the load is completely lost or the transmission line accident where the load is not lost, detecting that the effective force is zero and the reactive force is advancing is sufficient as a power load unbalance relay. It can function as

According to the present invention, the function as a power load unbalance relay can be achieved by simply looking at the effective force and the reactive power without providing a shunt reactor, so the economic effect is extremely large.

[Brief explanation of the drawing]

Fig. 1 is a system connection diagram of the generator, Fig. 2 is a flowchart of the present invention for detecting changes in effective cardiac force and reactive power, and Fig. 3
4 is a time chart showing changes in various quantities, and FIG. 5 is a flow chart of a conventional detection method. N...boiler, T...turbine, G...generator,
Pl ~ P5... Pipes through which steam flows, Po...
Water flow pipe, 13V... bypass valve, ■...
Oxidizing valve, CT...current transformer, PT...voltage transformer, T1+Tr2...transformer, CP...judgment section, CB, ~CB6...breaker, L, , L2
...Power transmission line, C1, C2...Capacitance, S...Sensor system. Agent Patent Attorney Akifusuke Takahashi 3 Bacteria

Claims (1)

[Claims] 1. A first means for detecting whether the difference between the active power of the turbine output and the generator output, which is determined based on the turbine output, the active power and the reactive power of the generator, is equal to or greater than a predetermined value; a second means for detecting whether a time change in effective cardiac force of the generator output is greater than or equal to a predetermined value; and detecting whether reactive power of the generator output is in phase advance. and a third means, when the first and second means both exceed the predetermined constant value and the third means notices that the reactive power is advancing, the generator A power load unbalance relay comprising means for detecting a load loss accident.