JP3230241B2 - Modulation equipment protection relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay for protecting a phase adjusting device having a filter for removing harmonics.

[0002]

2. Description of the Related Art In a place where a large amount of high-frequency current is generated as represented by a frequency conversion station, a phase adjusting device is installed in parallel with the ground in order to absorb a harmonic current. The phase modulating equipment is a combination of a dedicated filter for removing a single frequency and a dual-purpose filter for simultaneously removing a plurality of harmonics.
The first and thirteenth harmonics are respectively removed by a dedicated filter, and higher harmonics are removed by a combined filter.

[0003] The above-mentioned dedicated filter and dual-purpose filter are provided with a heat capacity corresponding to the power of the expected harmonic wave. The resistor and the reactor may be heated and overloaded. Therefore, a phase adjustment equipment protection relay is provided to protect these phase adjustment equipment.

[0004] In this case, it is important to detect and operate the phase adjustment equipment protection relay. Conventionally, as shown in FIG. 2, a ground transformer GPT is connected to a bus to detect a voltage. That is, when the bus voltage rises, it can be determined that an overcurrent is flowing through the phase adjustment equipment. Therefore, an overvoltage relay OV is provided to monitor the voltage, thereby protecting the phase adjustment equipment.

[0005]

However, there is a problem in that even if monitoring by voltage, a change in voltage is only small compared to a change in current, so that accurate detection cannot be performed. Of course, the above problem can be solved if the current flowing through the filter can be directly measured. However, it is generally difficult to insert a sensor for measuring the current because the filter is integrated into one sealed housing.

In general, discharge coils DL1 and DL2 for discharging electric charges (equivalent to tens of thousands of volts) of the capacitors C1 and C2 when the filters are disconnected by the switch CB2 are connected in parallel to the capacitors C1 and C2 constituting the filter. It is connected to the. Further, the discharge coils DL1, DL
2 are provided, and a voltage balance detection circuit VB is provided for monitoring the difference voltage between the windings ML1 and ML2 and judging an element failure.

The present invention has been made in view of the above problems, and has as its object to provide a filter in which a capacitor and a reactor are connected in series, and discharge the charge of the capacitor to the capacitor. It is an object of the present invention to provide a phase adjustment equipment protection relay capable of accurately protecting a phase adjustment equipment provided with discharge coils in parallel with a simple configuration.

[0008]

To achieve the above object, the present invention provides a phase protection equipment protection relay comprising: a current detecting means for detecting a current flowing through a filter; and an effective value calculation based on an output of the current detecting means. Operation processing means, and command means for outputting a circuit breaker command signal if it is determined that the operation processing means has detected an effective value exceeding a threshold value, wherein the current detection means detects a voltage applied to the discharge coil. The current flowing through the filter is detected by voltage measuring means for measuring, and differentiating means for converting a voltage value measured by the voltage measuring means into a current value.

[0009]

The capacitor constituting the filter is provided in parallel with a discharge coil for discharging the electric charge of the capacitor to prevent danger when the switch is turned off. Therefore, the present invention utilizes this discharge coil. Then, the terminal voltage of the capacitor is measured, converted into a current value by a differentiation process, and the current flowing through the entire filter is detected. Then, an effective value is calculated based on the detected current value to evaluate the heat loss of the filter. If it is determined that an effective value exceeding the threshold value is detected, a circuit breaker command signal can be output.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a circuit diagram of a phase adjusting device connected in parallel to a system bus and a protection relay 1 for protecting the phase adjusting device. The phase adjustment equipment consists of a switch CB2 and capacitors C1 and C2.
And a reactor 2 having a filter 2 formed of a series circuit. Capacitors C1, C2 and reactor L
Are arranged in series because they have high impedance with respect to the fundamental wave and low impedance with respect to the harmonics.

The terminals of capacitors C1 and C2 are discharge coils D
L1 and DL2, and discharge coils DL1 and DL2 have
Measurement windings ML1 and ML2 are provided. The phase adjustment facility protection relay 1 is connected to one of the windings (the winding ML1 in the embodiment).
), A voltage conversion transformer PT, a capacitor C, a resistor R, and an operational amplifier OP.
A sample-and-hold circuit 11, an A / D conversion circuit 12, an effective value calculating circuit 13 for calculating an effective value, and a sampler hold circuit 11, which samples 2r one cycle of the fundamental wave, compares the calculated effective value with a threshold value, and outputs a circuit breaker command signal. Output level judgment circuit 1
4. It consists of a timed circuit 15 and the like.

The differentiating circuit 10 outputs a signal proportional to the current flowing through the capacitor C1 by differentiating the voltage value appearing at the winding ML1. The effective value calculation circuit 13 calculates the current value im (m is 0
Using integer) to 2r-1 from the effective value, and requests the digital calculation of I = [(1 / 2r) Σim 2] 1/2. The effective value is determined because the heat loss in the reactor L and the like can be properly evaluated.

The level determination circuit 14 issues a command output when it receives an effective value equal to or larger than a threshold value for a predetermined time counted by the time limiter circuit 15. Note that the level determination circuit 14 may output a command if it determines that the value obtained by integrating the effective value input over a certain period of time is equal to or greater than a threshold value. According to the phase adjustment equipment protection relay having the above configuration, the effective value is measured by measuring the value corresponding to the current flowing through the filter 2 using the existing discharge coils DL1 and DL2 connected to the capacitors C1 and C2. By performing the calculation, an overload applied to the filter 2 can be detected.

The present invention is not limited to the above embodiment. For example, in this embodiment, the effective value is calculated by sampling and digitally converting, and then the digital value is used to obtain the effective value. , Rectified by a bridge rectifier circuit, and then passed through a square-fold circuit with diodes,
RMS / DC converter using operational amplifier (Burr Br
own, 4340 etc.) can also be used. In addition, various design changes can be made without departing from the scope of the present invention.

[0015]

As described above, according to the present invention, the terminal voltage of a capacitor is measured using a discharge coil connected in parallel with the capacitor of the filter, and converted to a current value by a differentiation process. The current flowing through the whole can be detected. Therefore, the overcurrent flowing through the filter can be accurately detected without adding a current transformer (CT), so that the phase adjustment equipment can be monitored and protected with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a specific configuration of a protection relay provided in a phase adjustment facility.

FIG. 2 is a block diagram showing a specific configuration of a phase adjustment facility.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 phase modulation equipment protection relay 2 filter 10 differentiating circuit 13 effective value calculation circuit 14 level judgment circuit C1 capacitor DL1 discharge coil ML1 measurement winding

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02H 7/00 H02H 3/08 H02J 3/01

Claims (1)

(57) [Claims] 1. A relay for protecting phase-modulating equipment, comprising a filter in which a capacitor and a reactor are connected in series, wherein the capacitor is provided with a discharge coil for discharging electric charge of the capacitor. Current detection means for detecting a flowing current; arithmetic processing means for calculating an effective value based on the output of the current detection means; and a circuit breaker command signal if the arithmetic processing means determines that the effective value exceeds a threshold value. Command means for outputting a voltage, and wherein the current detecting means includes a filter using voltage measuring means for measuring a voltage applied to the discharge coil, and differentiating means for converting a voltage value measured by the voltage measuring means into a current value. A phase protection equipment protection relay for detecting a current flowing through a relay.