Contact abnormality detecting system

• US 4,975,800 A
• Filed: 03/10/1989
• Issued: 12/04/1990
• Est. Priority Date: 03/14/1988
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Oshita, Youichi, Inui, Yoshiaki, Hashimoto, Akira, Kurosawa, Yukio, Yamagiwa, Tokio
• Primary Examiner(s): DEBOER, TODD
• Application Number:
  US07/321,382
• Time in Patent Office: 634 Days
• Field of Search: 361/111, 361/1, 361/113, 361/85, 361/182, 340/638, 340/644, 340/658, 324/520
• US Class Current: 361/113
• CPC Class Codes: G01R 31/3274 Details related to measuring, e.g. sensing, displaying or computing; Measuring of variables related to the contact pieces, e.g. wear, position or resistance measuring contact resistance G01R27/205
• CPC Class Codes: H01H 11/0062 Testing or measuring non-electrical properties of switches, e.g. contact velocity monitoring contacts H01H1/0015; monitoring gas density H01H33/563; monitoring vacuum H01H33/668; calibrating H01H69/01; adjusting H01H71/74; testing of electrical properties G01R31/333
• CPC Class Codes: H02H 3/50 responsive to the appearance of abnormal wave forms, e.g. ac in dc installations

Abstract

A contact abnormality detection system for use in a gas-insulated switchgear or other power transmission or distribution apparatus. A gas-insulated switchgear includes a hermetic housing, an insulating gas sealed in the housing, and conductors in the housing having contacts for providing a path for a large current and being electrically insulated from the housing. An abnormality in the contacts causes the contacts to generate vibrations when a large current flows through them. A vibration detector detects vibrations generated by the switchgear including the vibrations generated by the contacts. The frequency spectrum of the vibrations detected by the vibration detector is analyzed to detect if the vibrations contain frequency components in the range of 200 to 500 Hz which meet predetermined criteria. If the vibrations do contain such frequency components, a contact abnormality decision unit decides that the contacts exhibit a contact abnormality, thereby permitting the abnormality to be identified before the contacts fail.

Claims

1. A contact abnormality detection system for use in a power transmission or distribution apparatus comprising a hermetic housing and conductors in the housing having contacts for providing a path for a large current and being electrically insulated form the housing, the contact abnormality detection system comprising:

vibration detecting means for detecting vibrations generated by the power transmission or distribution apparatus, wherein the vibrations comprise vibrations generated by the contacts when the contacts exhibit a contact abnormality and a large current flows through the contacts exhibiting the contact abnormality;

vibration analyzing means for detecting if the vibrations detected by the vibration detecting means have a frequency component within a predetermined frequency range; and

contact abnormality decision means for deciding that the contacts exhibit a contact abnormality when the vibration analyzing means detects that the vibrations detected by the vibration detecting means have a frequency component in the predetermined frequency range.

2. A contact abnormality detection system according to claim 1, wherein the power transmission or distribution apparatus is a gas-insulated switchgear, and further comprises an insulating gas sealed in the housing.

3. A contact abnormality detection system according to claim 2, wherein the frequency component detected by the vibration analyzing means within the predetermined frequency range is at a frequency which is an integral multiple of a fundamental frequency of a current flowing through the contacts.

4. A contact abnormality detection system according to claim 3, wherein the predetermined frequency range is 200 to 5000 Hz.

5. A contact abnormality detection system for use with a gas-insulated switchgear comprising a hermetic housing, an insulating gas sealed in the housing, and conductors int he housing having contacts for providing a path for a large current and being electrically insulated form the housing, the contact abnormality detection system comprising:

vibration detecting means for detecting vibrations generated by the gas-insulated switchgear, wherein the vibrations comprise vibrations generated by the contacts when the contacts exhibit a contact abnormality and a large current flows through the contacts exhibiting the contact abnormality;

vibration analyzing means for detecting if the vibrations detected by the vibration detecting means have a frequency component within a predetermined frequency range of 200 to 5000 Hz by detecting one of a peak value and an average value of frequency components within the predetermined frequency range at frequencies which are integral multiples of a fundamental frequency of a current flowing through the contacts; and

contact abnormality decision mean for deciding that the contacts exhibit a contact abnormality when the vibration analyzing means detects that the vibrations detected by the vibration detecting means have a frequency component within the predetermined frequency range.

6. A contact abnormality detection system for use in a gas-insulated switchgear comprising a hermetic housing, an insulating gas sealed in the housing, and conductors in the housing having contacts for providing a path for a large current and being electrically insulated form the housing, the contact abnormality detection system comprising:

vibration detecting means for detecting vibrations generated by the gas-insulated switchgear, wherein the vibrations comprise vibrations generated by the contacts when the contacts exhibit a contact abnormality and a large current flows through the contacts exhibiting the contact abnormality;

comparing means for comparing a first frequency component of the vibrations detected by the vibration detecting means within a predetermined frequency range to a second frequency component of the vibrations detected by the vibration detecting means within the predetermined frequency range, wherein the first frequency component is at a first frequency which is an even integral multiple of a fundamental frequency of a current flowing through the contacts and the second frequency component is at a second frequency which is between the first frequency and a third frequency adjacent to the first frequency which is an odd integral multiple of the fundamental frequency; and

contact abnormality decision means for deciding that the contacts exhibit a contact abnormality when a ratio of the first and second frequency components compared by the comparing means exceeds a predetermined value at least equal to two.

7. A contact abnormality detection system according to claim 6, wherein the predetermined frequency range is 200 to 5000 Hz.

8. A contact abnormality detection system for use in a gas-insulated switchgear comprising a hermetic housing, an insulating gas sealed in the housing, and conductors in the housing having contacts for providing a path for a large current and being electrically insulated from the housing, the contact abnormality detection system comprising:

vibration detecting means for detecting vibrations generated by the gas-insulated switchgear, wherein the vibrations comprise vibrations generated by the contacts when the contacts exhibit a contact abnormality and a large current flows the contacts exhibiting the contact abnormality;

comparing means for comparing one of a peak value of first frequency components of the vibrations detected by the vibration detecting means within a predetermined frequency range of 200 to 5000 Hz to a minimum value of second frequency components of the vibrations detected by the vibration detecting means within the predetermined frequency range and an average value of the first frequency components to an average value of the second frequency components, wherein the first frequency components are at first frequencies which are even integral multiples of a fundamental frequency of a current flowing through the contacts and the second frequency components are at second frequencies which are between the first frequencies and third frequencies adjacent to the first frequencies which are odd integral multiples of the fundamental frequency; and

contact abnormality decision means for deciding that the contacts exhibit a contact abnormality when a ratio of the values compared by the comparing means exceeds a predetermined value greater at least equal to two.