Ground fault overvoltage relay device

Patent metadata

Field	Value
Publication number	US-10714924-B2
Application number	US-201515574108-A
Country	US
Kind code	B2
Filing date	Jun 11, 2015
Priority date	Jun 11, 2015
Publication date	Jul 14, 2020
Grant date	Jul 14, 2020

Abstract

A ground fault overvoltage relay device is configured to: determine whether or not a first condition is satisfied, the first condition being that at least two of line voltages between respective two phases are less than or equal to a first threshold value; determine whether or not a second condition is satisfied, the second condition being that a ratio between a minimum value of the line voltages between the respective two phases and a minimum value of the respective phase voltages is less than or equal to a second threshold value; determine whether or not a third condition is satisfied, the third condition being that the zero-phase voltage is greater than a third threshold value; and lock a ground fault detection output when the first condition is satisfied, or when the second condition is satisfied and the third condition is not satisfied.

First claim

The invention claimed is:

1. A ground fault overvoltage relay device, comprising:
an input unit configured to receive inputs of respective phase voltages of a power system detected by a voltage transformer;
a ground fault detection unit configured to detect a ground fault based on a zero-phase voltage calculated from the respective phase voltages;
a first determination unit configured to determine whether or not a first condition is satisfied, the first condition being that at least two of line voltages between respective two phases calculated based on the respective phase voltages are less than or equal to a first threshold value;
a second determination unit configured to determine whether or not a second condition is satisfied, the second condition being that a ratio between a minimum value of the line voltages between the respective two phases and a minimum value of the respective phase voltages is less than or equal to a second threshold value;
a third determination unit configured to determine whether or not a third condition is satisfied, the third condition being that the zero-phase voltage is greater than a third threshold value; and
a lock unit configured to lock a detection output by the ground fault detection unit, wherein the lock unit locks the detection output when the first condition is satisfied, and the lock unit locks the detection output when the second condition is satisfied and the third condition is not satisfied.

2. A ground fault overvoltage relay device, comprising:
an input unit configured to receive inputs of respective phase voltages of a power system detected by a voltage transformer;
a ground fault detection unit configured to detect a ground fault based on a zero-phase voltage calculated from the respective phase voltages;
a first determination unit configured to determine whether or not a first condition is satisfied, the first condition being that at least two of line voltages between respective two phases calculated based on the respective phase voltages are less than or equal to a first threshold value;
a second determination unit configured to determine whether or not a second condition is satisfied, the second condition being that a ratio between a minimum value of the line voltages between the respective two phases and a minimum value of the respective phase voltages is less than or equal to a second threshold value;
a third determination unit configured to determine whether or not a third condition is satisfied, the third condition being that a maximum value of the respective phase voltages is greater than a third threshold value; and
a lock unit configured to lock a detection output by the ground fault detection unit, wherein the lock unit locks the detection output when the first condition is satisfied, and the lock unit locks the detection output when the second condition is satisfied and the third condition is not satisfied.

3. The ground fault overvoltage relay device according to claim 1 , wherein the third determination unit starts determination of whether or not the third condition is satisfied when at least one of the respective phase voltages becomes more than or equal to a reference voltage value after a power failure in the power system.

4. The ground fault overvoltage relay device according to claim 1 , further comprising a receiving unit configured to receive information indicating closing of a transformer provided to the power system, wherein
the third determination unit starts determination of whether or not the third condition is satisfied when the information is received by the receiving unit.

5. The ground fault overvoltage relay device according to claim 3 , wherein
the third determination unit stops the determination of whether or not the third condition is satisfied when a predetermined time has elapsed from start of the determination, and
in a case where the determination is stopped by the third determination unit, the lock unit locks the detection output by the ground fault detection unit when the first condition or the second condition is satisfied.

6. A ground fault overvoltage relay device, comprising:
an input unit configured to receive inputs of respective phase voltages and a zero-phase voltage of a power system detected by a voltage transformer;
a ground fault detection unit configured to detect a ground fault based on the zero-phase voltage;
a first determination unit configured to determine whether or not a first condition is satisfied, the first condition being that at least two of line voltages between respective two phases calculated based on the respective phase voltages are less than or equal to a first threshold value;
a second determination unit configured to determine whether or not a second condition is satisfied, the second condition being that a ratio between a minimum value of the line voltages between the respective two phases and a minimum value of the respective phase voltages is less than or equal to a second threshold value;
a third determination unit configured to determine whether or not a third condition is satisfied, the third condition being that the zero-phase voltage is greater than a third threshold value; and
a lock unit configured to lock a detection output by the ground fault detection unit, wherein the lock unit locks the detection output when the first condition is satisfied, and the lock unit locks the detection output when the second condition is satisfied and the third condition is not satisfied.

7. A ground fault overvoltage relay device, comprising:
an input unit configured to receive inputs of respective phase voltages and a zero-phase voltage of a power system detected by a voltage transformer;
a ground fault detection unit configured to detect a ground fault based on the zero-phase voltage;
a first determination unit configured to determine whether or not a first condition is satisfied, the first condition being that at least two of line voltages between respective two phases calculated based on the respective phase voltages are less than or equal to a first threshold value;
a second determination unit configured to determine whether or not a second condition is satisfied, the second condition being that a ratio between a minimum value of the line voltages between the respective two phases and a minimum value of the respective phase voltages is less than or equal to a second threshold value;
a third determination unit configured to determine whether or not a third condition is satisfied, the third condition being that a maximum value of the respective phase voltages is greater than a third threshold value; and
a lock unit configured to lock a detection output by the ground fault detection unit, wherein the lock unit locks the detection output when the first condition is satisfied, and the lock unit locks the detection output when the second condition is satisfied and the third condition is not satisfied.

Assignees

• Mitsubishi Electric Corp

Inventors

• Matsumoto Tomoyoshi
• Oda Shigetoo
• Takemura Satoshi

Classifications

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title

• H02H3/26

  responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents · CPC title

• H02H3/353 Primary

  involving comparison of phase voltages · CPC title

• H02H3/165 Primary

  for three-phase systems · CPC title

• H02H3/083

  for three-phase systems · CPC title