IEEE C37.90-1989 pdf free.IEEE Standard for Relays and Relay Systems Associated with Electric Power Apparatus.
Abstract: ANSI/IEEE C37.90-1 989, IEEE Standard for Relays and Relay Systems Associated with Electric Power Apparatus, applies to relay systems that protect and control apparatus that generate, distribute and use electrical power. This standard defines service conditions and specifies relay performance requirements and performance information that relay manufacturers shall provide.
1. Scope
This standard applies only to relays and relay systems used to protect and control power apparatus. It does not cover relays designed primarily for industrial control, for switching communication or other low-level signals. or any other equipment not in tended for the control of power apparatus.
2. Purpose
The purpose of this standard is to specify standard service conditions, standard ratings, perftrmance requirements, and requirements for testing of relays and relay systems associated with power apparatus.
3. Definition of a Relay
A relay is an electric device designed to respond to input conditions in a prescribed manner and, after specified conditions are met, to cause contact operation or similar abrupt change in associated electric control circuits.
4. Relay Terms and Terminology and Classification by Function
Definitions of relay terms are not included in this standard. Refer to ANSI/IEEE C37.1 00-1981, Definitions for Power Switchgear, for definitions of relay terms. These terms are also included in ANSI/IEEE Std 100-1988. IEEE Standard
Dictionary of Electrical and Electronics Terms.
5. Service Conditions
5.1 Usual Service Conditions
Relays and relaying devices conforming to this standard shall be suitable for operation under the following conditions:
5.1.1 Ambient Temperature
This is the temperature of the air measured 30 cm from the outside surface of enclosures or covers of relay equipment.
This temperature shall be within the limits of—20 °C to 55 °C.
5.1.2 Relative Humidity
The average relative humidity may be up to 55% outside of enclosures or covers for temperatures up to 40 °C, with excursions up to 95% for a maximum of 96 h. without internal condensation.
5.1.3 Altitude
The usual condition of altitude shall be less than 1500 m.IEEE C37.90-1989 pdf free.