JPH0769353B2 - Actual load measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention is intended to perform a CT secondary circuit confirmation test in a device such as a switchboard using an insulation current transformer (CT). The present invention relates to an actual load measuring device.

(Prior art) At the start of operation of power system equipment, all devices (insulating current transformer (CT)) are used (protective relay board, control monitoring board,
In other distribution boards, etc., the current value of the CT secondary circuit and the phase angle of the PT secondary voltage reference are measured by the power load (actual load, actual power flow) as the final confirmation of the CT circuit, and the polarity of the CT circuit,
We are conducting confirmation tests as a system such as the direction of the protective relay and CT ratio.

As shown in FIG. 3, the conventional actual load measuring device 1 for conducting a system confirmation test using these CTs
The voltage V is taken from PT of R, S, T and CT of the transmission line R ', S', T '
In the protective relay panel 3 having the distance relay 2 that has taken the current I from the CT secondary test terminal T, T, the ammeter A
And a phase meter F are connected in series.

When measuring the actual load using the actual load measuring device 1, carefully operate the CT secondary test terminals T, T so that the CT circuit does not open, and place the CT2 on the measuring circuit.
The next current is passed and the current value and phase angle are recorded. When the measurement is completed, return the secondary test terminals T, T to their original positions and check that no current is flowing through the ammeter A. Remove the measurement lead wire and measure the next phase by the same operation. All the phases (R, S, T, N) were measured by repeating this measurement operation.

(Problems to be solved by the invention) Therefore, in the conventional actual load measuring apparatus 1, there is an error in the measurement circuit configuration, and a CT circuit open accident caused by an operation error of the CT secondary test terminals T, T occurs. The risks are probably included. In addition, since the phase switching by operating the CT secondary test terminals T, T was carefully performed, considerable work time was spent on actual load measurement. In some cases, the load (tidal current) changes during measurement, so the recording of each phase may vary, and it may be necessary to re-measure.

An object of the present invention is to provide an actual load measuring device that simplifies the CT secondary measurement circuit and develops a switch that does not open to shorten the working time.

[Structure of the Invention] (Means for Solving Problems) The actual load measuring device of the present invention is a secondary device for a CT in a switchboard or the like that uses an insulating current transformer CT and an instrument transformer PT in a power system. A shunt resistance inserted in series with each phase of the circuit, a fixed contact connected to both terminals of each shunt resistance of each phase, and a changeover switch having a changeover contact for selectively changing this with phase selection; And a phase meter for measuring the phase angle between the voltage of the shunt resistor of each phase generated by the phase selection of the changeover switch and the switching of the fixed contacts and the voltage using the secondary voltage of PT as the reference voltage. Is.

(Operation) In the present invention, when the actual load measurement is carried out, R, S, T,
It is possible to select the N phase and the fixed contact of the shunt resistor of each phase at the same time. Then, the phase angle can be measured by a digital phase meter which inputs the voltage of the shunt resistor and the voltage having the secondary voltage of PT as a reference voltage for each phase.

(Examples) The present invention will be described below with reference to examples shown in FIGS. 1 and 2. In FIGS. 1 and 2, the same reference numerals as those in FIG. 3 indicate the same parts, and thus the description thereof will be omitted.

First, referring to FIG. 1, the actual load measuring device 10 of the present invention is
This is applied to the protective relay panel 3 of 5KV transmission line, and the primary load current of 200A flowing through the transmission line R ', S', T'is 2000/5.
The current of the CT is changed to 0.5 A by the CT of A, and the secondary current of this CT is connected to the CT secondary test terminals T, T of the protective relay board 3 to configure the whole.

The actual load measuring device 10 is roughly divided into a switching operation unit 11 and a measuring unit 12, and the switching operation unit 11 and the measuring unit 12 are grouped in a single frame as shown in FIG. 2 and dedicated to each other. Used by connecting with code 13.

The switching operation unit 11 is the CT secondary test terminal T, T on the secondary side of the CT.
Is provided with a shunt resistor portion 14 connected to each phase and a changeover switch 15 for selecting the output voltage (50 mV) across the shunt resistor portion 14. Further, the measuring unit 12 converts the voltage of the switching operation unit 11 input via the dedicated code 13 into a current value and displays the current on the digital ammeter 16 and the secondary voltage of PT (V _RN = 63.5).
The voltage displayed by the digital voltmeter 17 with V) as the reference voltage is applied to the voltage-voltage phase meter 18 to measure the current value and the phase angle.

In the actual load measuring device 10 of the present invention configured as described above, the shunt resistor 14 is inserted in series for each phase at the secondary test terminals T, T of CT, and the fixed contacts, R → S, S → T, T → N, N is switched for each phase by the switching contact 15t, and the output voltage is digitally converted into a current value to be displayed numerically.

That is, in FIG. 1, the changeover contact of the changeover switch 15
When 15t is in the OFF, OFF position, the actual load measurement is not being performed. When the switching contact 15t is connected to the fixed contacts R, R, the R phase measurement can be performed. In this procedure, the switching contact 15t is changed to each fixed contact S, S → T, T →
By switching to N and N, the S phase, T phase, and N phase will be measured.

For each phase, the PT secondary voltage is used as a reference, and the phase with this low voltage is measured as the voltage-voltage phase by the high-sensitivity digital phase meter. In this method, the CT secondary current is not switched for each phase and the output voltage is switched, so there is no open accident in the CT secondary circuit due to the switching operation.

In the above example, the shunt resistance value is 0.5Ω (5A /
500mV) is used, the converted value is 50mV when the CT secondary current is 0.5A, and the display is a digital display of 0.50A. The phase meter 18 uses a high-sensitivity digital phase meter capable of measuring at 50 mV. The measurement error is ± 5 from the purpose of actual load measurement.
%, ± 5 degrees or less is sufficient. If it is necessary to further improve the accuracy, it is possible to increase the shunt resistance value and increase the output voltage.

As for the structure of the measuring device, the switching operation part 11 and the measuring part 12 are divided into a portable carrying type, and the connection is made efficiently and surely by using a dedicated cord 13 to make the measuring circuit structure, and the operability can be improved.

[Effects of the Invention] As described above, according to the present invention, since the shunt resistor inserted in series in each phase of the CT secondary circuit and the switching operation unit including the changeover switch for switching the shunt resistor and the measuring unit are provided, Reduction in CT circuit open accidents due to mistakes in the measurement circuit configuration, mistakes in operating the CT secondary test terminal during phase switching, simplification of the measurement circuit configuration, and improvement in handling workability with the changeover switch operation method reduces measurement work time. Labor saving is also possible.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a case where the actual load measuring device of the present invention is applied to a protective relay panel, FIG. 2 is a configuration diagram of the actual load measuring device, and FIG. 3 is a circuit diagram showing a conventional actual load measuring device. Is. 1, 10… Actual load measuring device 2… Distance relay 3… Protective relay board 11… Switching operation part 12… Measuring part 13… Special code 14… Shunt resistance 15… Selection switch 16… Digital ammeter 17… Digital voltmeter 18… Digital phase meter

Claims (1)

[Claims] 1. A shunt resistance inserted in series with each phase of a secondary circuit of the CT in a switchboard using an insulation current transformer CT and an instrument transformer PT in a power system, and a shunt resistance of each phase. Of the shunt resistance of each phase generated by the phase selection of the changeover switch and the changeover of the fixed contacts, the changeover switch having fixed contacts connected to both terminals of An actual load measuring device composed of a phase meter for measuring the phase angle between the PT and the voltage whose secondary voltage is the reference voltage.