Theory of Operation
A functional block diagram of the Form 6-LS recloser con-
trol is shown in Figure 3. Current sensing is provided by
three current transformers located in the recloser and inter-
faced to the Form 6 recloser 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 operation. Voltages for meter-
ing are connected to the analog input module through
terminal block TB8.
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 of
64 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/overvoltage, and under/overfrequency 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.
When the phase or ground current exceeds its pro-
grammed minimum-trip value and associated time-cur-
rent-curve (TCC) timing, the control initiates the pro-
grammed sequence of recloser tripping and reclosing
operations via the CPU and RIF modules. If the fault is
temporary, the control ceases to command recloser oper-
ations 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 (one trip on TCC1, one
trip on TCC2):
1. The overcurrent signal is integrated with time on the
selected curve for the first trip operation (TCC1) to pro-
duce the signal which energizes the trip circuit.
2. Energizing the trip circuit connects the supply 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 reclos-
er, and selecting the time-current characteristics for the
second trip operation (TCC2).
5. If current remains above the minimum-trip level, the
recloser will trip on TCC2 and lockout the recloser.
S280-70-10
5
TRIP SOLENOID
CLOSE SOLENOID
A Ø CT
B Ø CT
C Ø CT
OPEN / CLOSE
SWITCHES
CT COMMON
RECLOSER
POWER
24 VDC
BATTERY
INTERCON-
NECTION
BOARD
CPU
I/O
FRONT
PANEL
RS-232
(PROVIEW
PROTOCOL
ONLY)
TB7
TERMINAL
BLOCK
120/VAC
OUTLET
DUPLEX
ACCESSORY
TB8
TERMINAL
BLOCK
SENSING
VOLTAGE
INPUTS
3 inputs
USER
CONNECTIONS
5 outputs
8 inputs
USER
CONNECTIONS
8 outputs
MATCHING
TRANSFORMERS
AND SIGNAL
CONDITIONING
ANALOG INPUT
RIF
OPTICAL
ISOLATION
OPTICAL
ISOLATION
OPTICAL
ISOLATION
OPTICAL
ISOLATION
RS-232
IRIG-B
COMMUNICATIONS
BOARD ACCY
•
RS-485
•
FIBER-OPTIC
•
ETHERNET
TRANSFER
RELAY
SOURCE I
SOURCE II
INPUT
VOLTAGE
120 VAC
TEST
SWITCHES
Figure 3.
Form 6-LS pole mount recloser control operational flow diagram.
Figure 2.
Form 6-LS pole mount recloser control is accessible
from both the front and back of the cabinet.