Cooper Lighting S280-79-10 FORM 5 CONTROL DESCRIPTION

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SAFETY FOR LIFE

S280-79-10

FORM 5 CONTROL DESCRIPTION

Current sensing is provided by three current transformers located in the recloser and interfaced to the Form 5 control via the control cable. This cable also supplies Trip, Close, and Recloser status, and connects to the Recloser Interface (RIF) module to provide isolation for reliable opera- tion. Voltages for metering are also connected to the RIF module via the connector terminal block, TB-1 (Figure 3).

A functional block diagram of the Form 5 control is shown in Figure 3. Line current flowing through the recloser is converted by the CPU module to a digital signal suitable for metering and fault current calculations. Data sampling occurs at a rate 32 times per cycle. The CPU contains a data acquisition section that uses the acquired samples to compute the fundamental currents and voltage for use in overcurrent, under/over voltage and under/over frequency protection, as well as currents and voltages for metering functions. The current for overcurrent protection is calculated on a sub-cycle basis; it includes only the fundamental and DC component. For metering, the fundamental and harmonic current and voltages are determined.

When the phase or ground current exceeds its programmed minimum-trip value and associated time-current curve (TCC) timing, the control initiates the programmed sequence of recloser tripping and reclosing operations via the CPU and RIF modules. If the fault is temporary, the control ceases to command recloser operations after a successful reclose, and the control resets to the start of its operating sequence after a preset time delay. If the fault is permanent, the control performs its complete programmed sequence of reclose commands and locks out with the recloser open. Once locked out, the control must be closed via the operator panel or SCADA communications. This resets the control to the start of the operating sequence.

The following chain of events occurs for an operating sequence of two trips to lockout:

1.The overcurrent signal is integrated with time on the selected curve for the first trip operation (TCC1) to produce the signal which energizes the trip circuit.

2.Energizing the trip circuit connects the battery and capacitor to the trip solenoid to open the recloser.

3.Upon opening, the control starts timing on the first reclosing interval-delay time.

4.Upon expiration of this reclosing interval-delay, a clos- ing signal is issued from the control, closing the recloser and selecting the time-current characteristics for the second trip operation (TCC2).

5.If current remains above the minimum-trip level, the tripping and reclosing sequence is repeated.

6.The control begins the reset-delay timer if the over- current is cleared before the operating sequence reaches lockout indicated by a closed recloser and current below minimum trip.

7.When the reset-delay times out, the control is reset to the home state and is ready for another programmed operating sequence. If current rises above minimum trip prior to the reset-delay timing out, the timer is halted and the control resumes the operating sequence while the accumulated reset-delay timing is restarted.

TB1 TERMINAL BLOCK

RECLOSER

CUSTOMER

P.T. INPUTS

POWER SUPPLY

BATTERY

RIF

OPERATOR'S

TRIP SOLENOID

OPTICAL

CPU

DIF#1

DIF#2

ISOLATION

PANEL

(OPTIONAL)

(OPTIONAL)

CLOSE SOLENOID

OPTICAL

KEYBOARD

ISOLATION

OPEN / CLOSE

LED's

OPTICAL

LCD

SWITCHES

ISOLATION

A Ø CT

RS232 PORT

MATCHING

B Ø CT

TRANSFORMERS

C Ø CT

AND SIGNAL

CONDITIONING

RS232

12

12

12

12

Or

CT COMMON

FIBER-OPTIC

USER

USER

PORT

OPTIONS

CONNECTIONS

CONNECTIONS

RS232

6 unlatched outputs

6 unlatched outputs

Or

6 latched outputs

6 latched outputs

FIBER-OPTIC

12 inputs

12 inputs

PCB

Figure 3.

Form 5 control operational flow diagram.

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