JPS6016194A - Field circuit ground fault monitoring system - Google Patents

Abstract

PURPOSE:To prevent the erroneous judgement of a ground fault by starting a generator after controlling the temperature or moisture in a generator when becoming the operation value or higher of a field circuit ground fault protecting relay after a leakage current is started. CONSTITUTION:A computer 1 inputs a leakage current I, a temperature K in a generator, a moisture M in the generator and a starting command time t0, and discriminates whether it reaches the top value of a field ground fault protection relay or not after the current I is started at a time t0 on the basis of the temperature K and the moisture M. When discriminated that it reaches the top value, a start command B is fed to device group such as a space heater, and a dehumidifier, thereby controlling so that the leakage current becomes the top value or higher. Then, a main machine starting command A is fed. Thus, the erroneous operation of a field circuit ground fault protecting relay can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to detecting a ground fault in a field circuit of a power plant in advance and preventing it from causing a trip.

[Background of the invention]

Power plants, especially hydroelectric power plants, are characterized by the ability to quickly and accurately start and stop the main engine.

In particular, large-capacity pumped storage power plants in recent years are required to be able to reliably and quickly perform the process from start-up command to power generation operation as a backup in case a thermal or nuclear power plant fails to achieve the required output due to some kind of malfunction. Due to the geographical conditions of the construction site and the centralization of operation control, these hydroelectric power plants are becoming increasingly large in size, and each water system is now controlled remotely and centrally from a master control center. However, in order to maintain stable operation of a hydroelectric power plant, maintenance personnel must conduct periodic inspection inspections, as has been done in the past.

In order to save labor during maintenance and inspection, there is an extremely strong desire to automate daily patrol inspection work, add equipment abnormality diagnosis functions to this, and prevent accidents from occurring.

By the way, a trip sequence is set up in order to completely prevent the main engine from being destroyed if the abnormal operation continues for a long time by the protection relay, which has the mission of ultimate protection of the main engine. However, when this trip sequence is activated, the main engine cannot be started until the cause of the trip is removed, making it impossible to generate power quickly and reliably, which is the mission of a hydroelectric power plant. Particularly in unmanned power plants, it is difficult to recognize abnormal operation and avoid trips before the trip sequence is activated. One of the major causes of this trip is a field circuit ground fault.

Field circuit ground fault protection relays are used when the insulation of the field circuit is destroyed,
This protects against ground faults that could lead to damage to the main engine. Specifically, when the ground fault current exceeds a certain value, the protection relay determines that there is an abnormality and trips it. Incidentally, when the main engine is stopped, dust and the like often adhere to the creeping parts of the field circuit, and this dirt often absorbs moisture.

In this case, if the main engine is started as it is, a minute current will flow and it will often be mistakenly judged as a ground fault, and it is almost impossible to distinguish and detect this phenomenon from the original ground fault phenomenon. In order to eliminate the cause of this misjudgment, it is possible to dry the area around the field circuit using a space heater, dehumidifier, etc. to remove moisture and make it difficult for the minute current to flow, but it is most effective to do this just before startup. It is true. However, since the startup command time cannot be predicted, the timing of starting and stopping space heaters, etc., currently relies on the judgment of experts, and no appropriate processing method is in place.

As power plants become increasingly unmanned, there has been an increasing demand for detecting field circuit ground fault malfunctions before full activation, taking appropriate action, and even automatic recovery.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the prior art, fully automatically monitor ground faults in the field circuit, and completely prevent erroneous ground fault judgments, thereby starting and stopping a power plant quickly and reliably.

[Summary of the invention]

In the present invention, the change in leakage current after startup is predicted, and when the leakage current exceeds the operating value of the field circuit earth fault protection relay, for example, a space heater is activated as a preliminary process.

[Embodiments of the invention]

An example of the present invention is shown below.

FIG. 1 shows a configuration diagram of a monitoring system according to the present invention.

The input data required for the computer 1, which is the core of this system, are the leakage current value, the generator internal temperature, and K.

There is a humidity M inside the generator, and a main engine start command time to from a remote control station. Among these, the values of analog data I and M are input to the computer 1 via the converter 10 from the output signal of a sensor provided in the hydroelectric power generation equipment 11. Further, the main engine start command time to is inputted from a remote control center through the entire communication control section 1.

The computer 1 has a CPU 2 as its core, and a memory 3 in which system programs are stored. Memory for storing all data 4.
Communication control unit that exchanges data with a remote control center 5. The analog data 1. Analog input section 7 for inputting M to
．． Digital input section 8 for inputting digital data. The data is transferred from a digital output unit 9 that outputs digital data, and is transferred via a computer internal interface bus 6.

FIG. 2 shows the field circuit and ground fault detection circuit.

ACG is a generator, 14 is a field circuit, 13 is a field breaker,
12 is a ground fault protection relay that detects a field circuit ground fault and starts a trilag sequence. Further, ro is the field insulation resistance, and exhibits a resistance value of several MΩ or more under normal conditions. Inside the protection relay 12, there are a circuit protection relay contact Xl and a ground fault detection resistor r, which are connected to the relay coil X. This detection circuit is always connected to an external alternating current source AC via a rectifier 15.
Allow rectified direct current to flow. Since one end of the protective relay 12 is grounded and the other end is connected to the field circuit, if the field insulation resistance rQ is large, almost no current i will flow through this circuit. However, if a ground fault occurs in the field circuit, rQ becomes small, leakage current i becomes large, relay coil X is excited, and relay contact XI l field circuit breaker 13
e)! It will make J Tsubu. In the present invention, a leakage current detection series resistor r1 is newly added in series to this conventional circuit as an input source for the monitoring system, and a value measured by this rl is converted to an input level of a computer by a converter TI. In this way, first, the leakage current value It is inputted into the calculator.

FIG. 3 shows the measurement points of temperature and humidity M inside the generator, which are other input data. ACG is a generator, F is a main shaft, and E is a water turbine. There is a rotor 17 inside the ACG. Field coil 1
8, and there is space in the internal cavity to accommodate the internal cavity fan G'. Since the field circuit is located within the ACG, a temperature and humidity measuring device 16 is installed within the generator cavity to accurately measure ambient temperature and ambient humidity. Measured values are extracted from this and input into a computer via a separate external converter T2k.

In addition, another input data is the main engine startup time t. is input as a digital input signal that turns ON in response to a main engine start command from a remote location, and is used as the start timing for starting all calculations of a computer, for example. The input data is entered into the computer 1 online as described above, but in addition, the setting value (PI) g related to the leakage current i of the relay that causes the protective relay 12 to trip is also required, as shown in FIG.
It is stored in advance in the data memory 4 shown in FIG.

Next, FIG. 4 shows how the leakage current value i changes after startup. In Figure 4, the vertical axis is the leakage current value i, and the horizontal axis is 1=
1. This is the elapsed time since the main engine was started. Now, taking curve 16 as an example, the current value when the main engine is stopped is il, but after the start of operation, the leakage current i shows a tendency to increase and increases to a maximum value of 12. Thereafter, as the operation continues, the leakage 118i gradually decreases. For example, if the detection judgment value (PI)j of the protection relay is (PI:ljt), in this example, even though there is no actual ground fault, after the main engine starts up, due to a misjudgment, ? ) leading to the IJ tube sequence. However, if the initial value of the leakage current i decreases, a curve like 17.18 will be obtained, and a trip error will not occur. The shape of this curve group 16, 17° 18 is determined by the parameter P determined from the temperature inside the cavity and the humidity M inside the cavity. In this way, since the shape of the curve differs depending on the parameter P, it is possible that a trip will occur even if the leakage current value i is small.

Therefore, if the value of P and the value of ■ are known before the start of operation, it is possible to detect whether the shape of the curved edge is breaking or causing a trip.

FIG. 5 is a diagram showing the relationship between temperature, humidity M, and parameter P. P is determined in this manner, with the tendency for P to be larger as temperature K is more sieve and humidity M is lower, and P tends to be larger as K is lower and M is higher.

The flowchart shown in FIG. 6 is stored in the system program memory 3 of the computer 1 in FIG. 1 in the form of a program. This system operates, controls and monitors according to the flowchart shown in FIG. The operation will be explained below. Note that the numbers below and the numbers in FIG. 6 match.

(1); The computer constantly detects whether there is a start command t0 for the main engine. If detected, the time is stored in the data memory 4.

(■); Input all the data required for subsequent calculations.

I, M are transducers T1. pl with data via T2
Further, regarding the detection judgment value (PI) j of the protection relay 12, data stored and set in the data memory 4 in advance is input.

(DI) ; P is a parameter of K and M, and K and M
Using the curve shown in Figure 5, determine P'(■)
; Data representing characteristic curves of different types of P is stored in the data memory 4 (9). The mechanism is shown in Figure 7. The vertical axis is assigned the value of the parameter P+ determined in FIG. 5, and the horizontal axis is assigned the time t, forming a kind of matrix group. When P+ is determined in (III), pointer H is searched for a column corresponding to Pl.

In that column, the coefficient Ptm of Pl at each time after startup is recorded. The above memory contents Pg to P1m are extracted.

(V): When the leakage current value is multiplied by Pt1 to Ptm, the characteristic curve 16.1 regarding leakage current corresponding to Fig. 4 is obtained.
7.18 is determined. IXP*t on actual memory
#lXPt1, . . ., the value of engineering×Pta is stored.

(■); Find and extract the maximum value among these I x Ptm, the data of distortion 2 in Figure 4.

(■); This data is the trip value (P
I: Determine whether it is greater than +4.

(■); (I X Pt++ )whx≧(PI)a
If it is started as it is, a trip is expected, so it is necessary to lower the value of MmX (I X Ptm ).

For this (10), send a startup command Bk to equipment such as space heaters and dehumidifiers (I return.

Note that a timer not shown in the diagram measures the time from the start of this program, and if the program does not end after a certain period of time, there may be a space heater malfunction, a malfunction of the converter, sensor, etc. Forcibly stop the program and issue an alarm.

(IX); If (IXPt-hAw<(PI:)*, no trip will occur even if the engine is started as it is, so immediately send the main engine start command A.

Furthermore, Figure 8 shows the installation of space heaters, dehumidifiers, etc. To reduce humidity around the field circuit, use a generator AC
It is best to install space heaters, dehumidifiers, etc. C inside G, but if this is not possible structurally, installing C under the ACG as shown in the example in Figure 8 will improve efficiency. It has a good dehumidifying effect. Space heating and dehumidification determined in (■) (11) The machine startup command B turns on the startup switch Ql and dehumidifies.

In the present invention, the determination is made when the main engine is started while the main engine is grounded, but even during operation, this system can measure and detect leakage current values completely online, so abnormalities that occur before the ground fault protection relay operates It can recognize trends in conditions and provide warnings and displays prior to every trip, allowing it to be developed into a preventive maintenance system. In this case, the system configuration will be the same hardware configuration as the present invention. As another alternative to the present invention, if it is expected that the protection relay will detect a ground fault after activation, the protection relay may be opened and locked at an appropriate time after activation.

〔Effect of the invention〕

In this way, in this embodiment, a series resistor r1 for leakage current detection is added to the current power plant equipment, temperature and humidity are input into the computer, and calculations are made according to the flowchart to protect the field circuit from ground faults. In addition to preventing relay malfunction, it also sends a command for self-recovery, making it possible to perform appropriate processing.

(12) According to the present invention, field circuit ground faults can be automatically monitored, erroneous ground fault judgments can be prevented, and self-recovery control can also be performed, thereby providing the effect of quickly and reliably starting up a power plant.

[Brief explanation of the drawing]

Figure 1 shows the configuration of the monitoring system, Figure 2 shows the field circuit and ground fault detection circuit, Figure 3 shows the locations where temperature and humidity are measured, and Figure 4 shows how the leakage current changes after startup. Figure 5
The figure shows the relationship between temperature, humidity, and parameter P, Figure 6 is a flowchart of the monitoring system, Figure 7 shows the state of data accumulation in memory, and Figure 8 shows the installation of space heaters, dehumidifiers, etc. . 1... Computer body, 2... CPU, 3... System program memory, 4... Data memory, 5...
Communication control section, 6... usi internal interface bus, 7... analog input section, 8... digital input section, 9... digital output section, 10... converter, 11
...Hydroelectric power generation equipment, 12...Field circuit ground fault protection relay, 13...Field circuit breaker, 14...Field circuit, 15
... Rectifier, rl (13) ... Series resistance for leakage current detection, T1 ... Converter, ■
...detection current, ACG...generator, r(,...field insulation resistance, Xl...relay contact, AC...alternating current power supply, X...relay coil, r...ground Fault detection resistance, i
...Leakage current, ■...Leakage current value, K...Temperature,
M...humidity, to...main engine startup time, (PI3 no.
...Relay operation judgment value. Agent Patent Attorney Akio Takahashi (14) 2m Figure 4 to g, frzt - to ((fJ

Claims (1)

[Claims] 1. It measures the field ground fault current in the generator field circuit, detects in advance that the ground fault protection relay will operate after starting the main engine, and starts the generator after controlling the temperature or humidity inside the generator. field circuit ground fault monitoring system.