Method for loose joint detection in medium voltage switchgears and medium voltage switchgear itself

Patent metadata

Field	Value
Publication number	US-2017148300-A1
Application number	US-201615353749-A
Country	US
Kind code	A1
Filing date	Nov 17, 2016
Priority date	Nov 19, 2015
Publication date	May 25, 2017
Grant date	—

Abstract

A method for loose joint detection in medium voltage switchgears with busbar joints, circuit breaker upper and lower spouts, and cable connection joints, arranged in an air insulated housing, and medium voltage switchgear itself, in order to create an effective loose joint detection with lower operating expense, but with high performance and accuracy, involves measuring actual temperatures at a first phase as a first temperature (T 1 ), at a second phase as a second temperature (T 2 ), at a third phase as a third temperature (T 3 ), at predefined critical points, such as at the busbar joints, and/or at the circuit breaker upper spouts, and/or at the circuit breaker lower spouts, and/or the cable connection; and comparing temperatures in a logical dependency Ti>(Tj+dT), with i≠j, permuted with i from 1, 2, 3, and j from 1, 2, 3, and setting the alarm if the logical dependency is fulfilled.

First claim

1 . A method for loose joint detection in a three phase medium voltage switchgear including busbar joints, circuit breaker upper and lower spouts, and cable connection joints, arranged in an air insulated housing, and several temperature measurement points, the method comprising:
measuring actual temperatures are measured at a first phase as a first temperature (T 1 ), at a second phase as a second temperature (T 2 ), at a third phase as a third temperature (T 3 ), at one or more predefined critical points; comparing the temperatures in a logical dependency:
Ti >( Tj+dT ),with i≠j,
permuted with i from 1, 2, 3
and j from 1, 2, 3; and

setting an alarm if the above condition is fulfilled.

2 . The method of claim 1 , wherein the critical points include a busbar joint, a circuit breaker upper spout, a circuit breaker lower spout, a cable connection, or a combination of two or more of any of these.

3 . The method of claim 1 , wherein the critical points include a busbar joint.

4 . The method of claim 1 , wherein the critical points include a circuit breaker upper spout.

5 . The method of claim 1 , wherein the critical points include a circuit breaker lower spout.

6 . The method of claim 1 , wherein the critical points include a cable connection,

7 . The method of claim 1 , wherein the alarm is set, based on an indication condition, if:
a loose joint in the first phase is indicated, wherein T 1 >(T 2 +ΔT) or T 1 >(T 3 +ΔT); and/or a loose joint in the second phase is indicated, wherein T 2 >(T 1 +ΔT) or T 2 >(T 3 +ΔT); and/or a loose joint in the third phase is indicated, wherein T 3 >(T 1 +ΔT) or T 3 >(T 2 +ΔT).

8 . The method of claim 7 , wherein the indication condition includes the loose joint in the first phase being indicated, wherein T 1 >(T 2 +ΔT).

9 . The method of claim 7 , wherein the indication condition includes the loose joint in the first phase being indicated, wherein T 1 >(T 3 +ΔT).

10 . The method of claim 7 , wherein the indication condition includes the loose joint in the second phase being indicated, wherein T 2 >(T 1 +ΔT).

11 . The method of claim 7 , wherein the indication condition includes the loose joint in the second phase being indicated, wherein T 2 >(T 3 +ΔT).

12 . The method of claim 7 , wherein the indication condition includes the loose joint in the third phase being indicated, wherein T 3 >(T 1 +ΔT).

13 . The method of claim 7 , wherein the indication condition includes the loose joint in the third phase being indicated, wherein T 3 >(T 2 +ΔT).

14 . The method of claim 1 , further comprising:
predefining a value range for ΔT; storing the value range in a control device; and reading all temperatures into the control device, the control device evaluating according to the logical dependency or if a loose joint in the first phase is indicated, wherein T 1 >(T 2 +ΔT) or T 1 >(T 3 +ΔT), and/or a loose joint in the second phase is indicated, wherein T 2 >(T 1 +ΔT) or T 2 >(T 3 +ΔT), and/or a loose joint in the third phase is indicated, wherein T 3 >(T 1 +ΔT) or T 3 >(T 2 +ΔT), thereby generating an alarm signal.

15 . The method of claim 1 , comprising:
storing all measured temperature values in a datafile, thereby enabling retrospective analysis of historical data.

16 . The method of claim 15 , further comprising:
automatically stearing and organizing the datafile as a shift register including an adjustable time frame or time slot.

17 . The method of claim 16 , wherein the time slot is also event triggered.

18 . The method of claim 17 , wherein a restropective time slot is also event triggered.

19 . A medium voltage switchgear, comprising:
a loose joint detector at one or more busbar joints, circuit breaker upper sprouts, circuit breaker lower spouts, and/or cable connection joints, arranged in an air insulated housing, carrying out the method of claim 1 ; temperature sensors arranged at joint points of the switchgear, at the busbar joints, at the circuit breaker upper spouts, at the circuit breaker lower spouts, at the cable connection joints, the temperature sensors being arranged at all three phases of the joint points and spouts each; and a central evaluation unit feed receiving all temperature sensors values, in order to calculate the logical dependency.

Assignees

• Abb Schweiz Ag

Inventors

• Stupak Marcel
• Kozel Tomas
• Scarpellini Massimo
• Magoni Stefano

Classifications

• H02B1/20

  Bus-bar or other wiring layouts, e.g. in cubicles, in switchyards (installations of bus-bars H02G5/00) · CPC title

• H02B1/04

  Mounting thereon of switches or of other devices in general, the switch or device having, or being without, casing · CPC title

• G01K13/00

  Thermometers specially adapted for specific purposes · CPC title

• H02B1/24

  Circuit arrangements for boards or switchyards · CPC title

• G01R31/3275 Primary

  Fault detection or status indication · CPC title