Apparatus for preventing and predicting deterioration of insulation in an electric equipment

• US 5,216,226 A
• Filed: 03/03/1992
• Issued: 06/01/1993
• Est. Priority Date: 03/04/1991
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Miyoshi, Kazuo
• Primary Examiner(s): Paschall, Mark H.
• Application Number:
  US07/845,022
• Time in Patent Office: 455 Days
• Field of Search: 219/203, 219/494, 219/497, 219/501, 219/505, 219/508, 219/499, 73/336.5, 324/505, 324/500, 324/537, 324/555, 340/602, 340/650, 340/655
• US Class Current: 219/497
• CPC Class Codes: F24F 11/00 Control or safety arrangements
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2110/20 Humidity
• CPC Class Codes: F24F 2140/30 Condensation of water from cooled air
• CPC Class Codes: H01H 1/62 Heating or cooling of contacts

Abstract

In an electrical equipment such as a control center, operation of space heaters is controlled on the basis of humidity detected by a humidity sensor plus a differential value of an effective value of leakage current flowing through insulating materials in the control center.

Claims

1. An apparatus for preventing and predicting deterioration of electrical insulation in electrical equipment, comprising:

a leakage current detector for detecting a leakage current flowing though insulating materials in said electrical equipment;

a sensor for detecting humidity in said electrical equipment;

a space heater mounted in said electrical equipment;

control means for controlling operation of said space heater in response to a first output signal based on said sensor and a differentiated value of an effective value of a second output signal based on said leakage current detector;

leakage-current measuring means which receives said second output signal and issues the effective value of said second output signal and the differentiated value of said effective value;

arithmetic judging means for issuing an output signal based on a result which is obtained by comparing said effective value and said differentiated value with respective predetermined values; and

indicating means for indicating a state of insulating performance of said insulating materials in response to said output signal of said arithmetic judging means.

2. An apparatus for preventing deterioration of electrical insulation in electrical equipment, comprising:

a leakage current detector for detecting a leakage current flowing through insulating materials in said electrical equipment;

a humidity sensor for detecting humidity in said electrical equipment;

a dew condensation sensor for detecting dew condensation in said electrical equipment;

a space heater mounted in said electrical equipment;

a first comparative judging circuit for selectively issuing a control signal for said space heater in response to output signals of said humidity sensor and said dew condensation sensor;

a second comparative judging circuit for selectively passing said control signal in response to a differentiated value of an effective value of leakage current detected by said leakage current detector; and

a heater control circuit for controlling said space heater in response to said control signal.

3. An apparatus for predicting deterioration electrical insulation in electrical equipment, comprising:

a leakage current detector for detecting a leakage current flowing through insulating materials in said electrical equipment;

a humidity sensor for detecting humidity in said electrical equipment;

a dew condensation sensor for detecting dew condensation in said electrical equipment;

a temperature sensor for detecting temperature in said electrical equipment;

first judging means which issues a signal for measuring a leakage current when at least one of humidity, dew condensation and temperature satisfies a predetermined condition with respect to a predetermined period or predetermined times;

leakage-current measuring circuit which measures a leakage current detected by said leakage current detector at every time of receipt of said signal and issues an effective value of said leakage current and a differentiated value of said effective value;

second judging means which issues an output signal when said differentiated value is equal to or more than a predetermined value and which issues said effective value;

alarm circuit for indicating a state of alarm when said output signal is received; and

a memory circuit for storing said effective value at every time when said effective value is issued from said second judging circuit.