Measuring system for continuously monitoring a high-voltage bushing

Patent metadata

Field	Value
Publication number	US-9557349-B2
Application number	US-201414762989-A
Country	US
Kind code	B2
Filing date	Jan 14, 2014
Priority date	Jan 23, 2013
Publication date	Jan 31, 2017
Grant date	Jan 31, 2017

Abstract

A measuring system for continuously monitoring a high-voltage bushing provides for multi-stage, secure protection. The system includes a measuring circuit, a connection plug, a connection cable, and a three-stage protective circuit. When overvoltages occur at the measurement connection, each protective stage can produce a short circuit at the measurement connection to limit the voltage. A first protective stage responds at a response voltage U 1 . A second protective stage connected between the first stage and the measurement connection responds at a higher response voltage U 2 . A low-pass filter in the first protective stage decouples the first and second protective stages. The first stage responds to overvoltages at operating frequency, the second stage responds to high-frequency overvoltages. A third protective stage is connected between the measurement connection and the first protective stage in parallel with the measurement connection and includes a mechanical switch for short-circuiting when a third response voltage is present.

First claim

The invention claimed is:

1. A measuring system for continuously monitoring a high-voltage bushing, the measuring system comprising:
a measuring circuit for monitoring the high-voltage bushing;
a connecting plug for connecting said measuring circuit to a measuring connection of the high-voltage bushing;
a connecting cable for connecting said measuring circuit to said connecting plug; and
a protection circuit for protecting said measuring connection from over voltages, said protection circuit being configured to establish a short circuit between a high-voltage terminal and a ground terminal of the measuring connection if an overvoltage occurs;
said protection circuit including a first protection stage, a second protection stage electrically connected in parallel with said first protection stage, and a third protection stage;
said first protection stage including a low-pass filter;
said second protection stage being disposed between the measuring connection and said first protection stage;
said first protection stage having a first response voltage and said second protection stage having a second response voltage greater than the first response voltage;
said third protection stage being connected in parallel with the measuring connection and disposed between the measuring connection and said first protection stage, and said third protection stage includes a mechanical switch for establishing the short circuit if a third response voltage is present.

2. The measuring system according to claim 1 , wherein said first protection stage has a circuit branch connecting the high-voltage terminal to the ground terminal and including a varistor or a suppressor diode.

3. The measuring system according to claim 1 , wherein said second protection stage has a circuit branch connecting the high-voltage terminal to the ground terminal and including a spark gap.

4. The measuring system according to claim 1 , wherein said third protection stage includes a series circuit of a spark gap, a rectifier, and a coil, and wherein said mechanical switch is switchable via a current flow through said coil and forms together with said coil a reed relay.

5. The measuring system according to claim 4 , wherein the reed relay is a bistable relay.

6. The measuring system according to claim 1 , wherein at least one of said first, second, and third protection stage is configured to be redundant.

7. The measuring system according to claim 1 , wherein said protection circuit is integrated into said connecting plug.

8. The measuring system according to claim 1 , wherein the high-voltage bushing being monitored is a high-voltage bushing of a power transformer.

Assignees

• Siemens Ag

Inventors

• Kutzner Ruediger
• Weber Marc

Classifications

• G01R31/1227 Primary

  of components, parts or materials (G01R31/1209, G01R31/1218, G01R31/18 take precedence; circuits therefor G01R31/14; testing vessels of electrodes G01R31/16) · CPC title

• G01R1/36 Primary

  Overload-protection arrangements or circuits for electric measuring instruments · CPC title

• G01R19/0092

  Measuring current only · CPC title