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Specification for Faulted Circuit Indicators


Edison Controls Faulted Circuit Indicators offer a number of electrical options to meet the changing requirements of modern distribution systems. More extensive use of reclosers, current limiting reactors, and phase correcting capacitor banks etc. make the selection and specification of Faulted Circuit Indicators (FCIs) more complex. Following is a general discussion of FCI features, a guide to the selection and specification of Edison Controls FCIs and a glossary of terms. If you have questions, please call or email us.

Range of Electrical Options and Specifications:

Single or Three Phase Units - A single phase FCI has a single current sensing core assembly and a single indicator viewing assembly. A three phase unit has three independent sensing cores and one indicator viewing assembly. Three phase units are designed for use on insulated cables in underground applications only.

Current or Voltage Powered Units - FCIs, single or three phase, are powered from the system line current, if the line current is greater than 0.5 amps. For applications where the line current may fall below 0.5 amps during any part of a 24 hour period, voltage powered units must be used.

Reset - Immediate or Delayed - FCIs are available with either immediate or timed reset. The immediate reset mode will reset the unit approximately 75 seconds after normal power is restored. The timed reset will delay the reset pulse for up to 72 hours after normal power is restored.

Inrush Restraint - FCIs are available with or without inrush restraint. Inrush restraint is often used to coordinate with reclosers and is available in two forms - dual trip and delayed trip. Dual trip is used when the inrush current is known. Delayed trip is used when the inrush current is not known or when it may vary over a 24 hour period.

Insulated or Non-Insulated Cables - For uninsulated cables a single phase hot stick unit must be used. For insulated cables either single phase hot stick units, remote indicating units, or three phase units may be used.

Trip Levels and Reset Levels - The trip and reset levels are system dependent and require a reasonable knowledge of operating parameters. The logic charts on pages 2 and 3 are useful in establishing the initial trip and reset levels.

General Specifications

Trip Level: 25 - 3000 A with repeat accuracy of +/- 10%
Reset Level: l.0A standard; 3.0A or 0.5A l00v/230V for secondary voltage reset unit.
Reset Time: resets automatically in one to four minutes after restoration,
unless timed reset is specified.
Trip Response: Normally 1 ms or less; (refer to trip response curve below)
Power requirements: Line powered
Adjacent Field Susceptibility: Immune to adjacent magnetic field tripping
Overload Capability: 40,000A peak per ANSI/IEEE 495-1986
Maximum Continuous Current (Non-trip State):
3.0A reset Models: 800A
1.0A reset Models: 300A
0.5A reset Models: 150A
Environmental Capability: Meets ANSI/IEEE 495-1986
Life Expectancy: 20 years

Trip Response Curves


Single Phase Unit - A single phase FCI has a single current sensing core assembly and a single indicator.

Three Phase Unit - A three phase single flag unit has three independent sensing cores and one indicator. The three sensors continuously monitor the current in all three phases and will show a trip indication on the meter if the trip current setting is exceeded on one or more phases. The unit will reset when current equal to or greater than the reset current level is present in all three phases.

The three phase three flag unit has three independent sensing cores and one indicator assembly that contains three flags. The flags are marked A,B,C and have a corresponding sensor. A flag will trip only when the corresponding sensor detects fault current and will not reset until the sensor detects normal current load. Each flag and sensor combination is independent of the other two.

Trip Level - The RMS current level at which the FCI is preset to switch the indicator to the "fault" or "tripped" position.

Reset - Returning the indicator to the "no fault" or non-tripped position. Primary or secondary line current of secondary line voltage maybe used to develop the reset pulse.

Reset Current - The current level required to return the indicator to the "no fault" or non-tripped position.

Continuous Current Rating - The maximum continuous current the FCI will sustain without damage for any period of time in excess of 5 minutes.

Inrush Restraint - A design option to prevent false tripping when energizing a dead line. This feature is of importance when coordinating with recloser devices. There are two design approaches - dual trip and delayed trip.

Dual Trip - Dual trip selects a higher trip level for the first 15 current cycles when a dead line is energized. This is used when the inrush currents are known and allows the inrush currents to decay before selecting the normal trip level for continuous monitoring.

Delayed Trip - Delayed trip inhibits the transfer of a "trip" pulse from the overcurrent detector to the meter driver for 15 (or 30) current cycles. This is used when the inrush currents are not known and the time delay allows the inrush currents to decay before the end of the delay interval.

Response Time - This is the time from the initiation of the fault to when the FCI can give an indication of fault. It is a difficult parameter to define accurately as it depends on the rate of rise of the fault current which in turn depends where on the current cycle the fault occurs and the magnitude of this current. In general the requirement for a fast response is to coordinate with fast acting current limiting fuses. The response curves should be compared to the fuse curves to ensure proper coordination.

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