SDR Vacuum Reclosers - LEKULE BLOG


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Tuesday, 19 January 2016

SDR Vacuum Reclosers

Recloser principle and design

Reclosers are used in distribution systems. Like circuit breakers, reclosers are used to make and break normal and fault currents. Reclosers are fully equipped with sensors and a controller to provide a means of protection and control. In case of a line fault, reclosers can break and make currents several times, thus avoiding longer network interruptions due to temporary faults.

Type SDR vacuum reclosers are outdoor devices designed for repeated opening and reclosing in case of a fault, as specified in ANSI/IEEE standard C37.60.

The vacuum recloser consists of two main components: the recloser switch and the control cubicle.

The manufacture, design and testing of the vacuum recloser is based on current regulations and standards and state-ofthe-
art technology. The product conforms to the following standards:

ANSI/IEEE C37.60/IEC 62271-111
IEC 60255-11
IEC 60255-21-1 Class I
IEC 60255-21-2 Class I
IEC 60255-21-3 Class I
IEC 60255-22-1 Class III
IEC 60255-22-2 Class IV
IEC 60255-22-3 Class III
IEC 60255-22-4 Class IV
IEC 60255-22-5
IEC 60255-22-6
IEC 60255-25
IEC 60255-5
IEC 62271-1
Note: IEEE C37.60 and IEC 62271-111 are the same document (dual logo IEEE and IEC).

Recloser switch unit with encapsulated vacuum interrupter:

The recloser switch unit is comprised of the poles, the operating mechanism and the operating mechanism housing. The
side sections with the support feet form the base of the recloser switch unit. The switch unit can be secured to the pole mounting or substation frame. 


The poles are molded using cycloaliphatic epoxy resin specially designed for outdoor use. The vacuum interrupters are encapsulated
in the pole units. In addition, each pole contains a current transformer and may also contain an optional voltage sensor.

The sequence of the poles is C - B - A(sequence left to right when  viewed from the lower terminal side of the recloser
switch unit - rear of recloser) (refer to Figure 4). This is marked on the operating mechanism housing by identification indents (A = 1 indent, B = 2 indents and C = 3 indents). This sequence identifies the currents IA, IB and IC of the controller.

Current transformers (CTs)
The type SDR vacuum recloser is equipped with one integrated current transformer per pole. The current transformer is the
conventional type (iron core magnetic) and has a ratio of 800 A:1 A. It is for protection purposes and optimized for operation with the controller (see control cubicle on page 13). The secondary signal
is based on IEC 60044-1. The secondary wires of the CT are
connected to a varistor for each pole in the switch unit. This prevents the occurrence of high voltages (due to open-circuit CT
secondary) if the control cable is removed while the switch unit is in operation. Do not disable the varistor circuit.
The signal transfer from the CTs to the controller is by the control cable. A separate cable is not required.

Voltage sensor (optional)

The SDR vacuum recloser can be equipped with integrated resistive voltage sensors (optional). The integrated resistive voltage
sensors have a high level of accuracy and are used both for measurement and protection purposes. The ratio is adapted
to operation with the controller (see control cubicle on page 13) and provides a 110 V/√3 secondary signal with rated primary voltage applied to the recloser. No other controller should be used for the voltage measurement as the sensor design and controller design are coordinated. An optional separate sensor cable equipped
with special screening (shield) is used for the signal transfer from the voltage sensors to the controller. This results in a high level of accuracy and protection against disturbances. The sensor cable is connected at the back of the operating mechanism housing next to the control cable.

The secondary wires of the voltage sensors are connected to a varistor for each pole in the switch unit. This prevents the
occurrence of high voltage on the sensor cable if the sensor cable is removed while the switch unit is in operation. Do not disable the varistor circuit.

Operating mechanism
The operating mechanism for the vacuuminterrupters is located in a  metal housing.
To meet the required fast reclosing cycles, a magnetic actuator with capacitors as energy storage drives the switch unit. A gang-operated mechanism connects the magnetic actuator with the vacuum interrupters.
The operating mechanism is equipped with anti-condensation space heaters. It is operated together with the heating in the control cubicle and controlled by a thermostat.
A mechanical position indicator is easily visible from the ground and shows the current switch position of the recloser
(open = green, closed = red). The colored display is reflective in the dark when using a flashlight.

Lockout handle
A lockout handle with ring protrudes from the operating mechanism housing. The ring is colored bright yellow and is therefore easily seen.
By pulling the lockout handle, the recloser opens and remains locked in this position. The locking has a dual electrical effect; it
locks out both the controller and the electronics. It also mechanically locks the magnetic actuator.
As long as the lockout handle is pulled out, it is not possible to close the switch unit electrically, whether locally or from a
remote location. The interlocking is not reset until the lockout handle has been completely pushed in. After this, the
switch unit can be closed electrically, either locally or from the control room.
The switching is described in the Operation section of this instruction manual (see page 28).
Note: The lockout handle must be fully pushed in or the interlocking will prevent closing of the recloser.

Operations counter
A mechanical operations counter is installed at the bottom of the recloser switch unit. It records the total number of switching operations independently of the electrical recording in the controller. The operations counter is used to keep track of the total number of operations of the switch unit in case the controller is replaced or the electronic counter is reset in the controller.

Pole-mounting frames

A pole-mounting frame is used to install the recloser switch unit on an overhead
line pole. The mounting frames can also optionally accommodate surge arresters
and source side external voltage sensors.

The following pole-mounting frames are

Design 1 with provisions for line-side external voltage sensors and line- and load-side surge arresters (see Figure 9) Design 2 with provisions for load-side surge arresters (see Figure 10).

It is recommended that at least two 0.75 inch bolts be used as king bolts to secure the pole-mounting frame to the pole.

For installing within substations, a special frame is available (see installing at the substation on page 23).

Control cubicle
The control cubicle is equipped with integrated pole-mount brackets. It can be installed on the recloser pole or substation
frame at an operating height as preferred by the user.
The control cubicle is equipped with a lockable door with provision for a padlock.
Behind the door is a swing frame, which contains the controller, miniature circuit breakers and a general power outlet (GPO)
for a laptop. Behind the swing frame, there are printed circuit boards (PCB), rechargeable batteries and wiring connections.

The control cubicle is equipped with a thermostat-controlled anti-condensation heater (space heater). The thermostat also
controls the space heater in the switch unit. Each heater consists of two resistors.

The heating is switched off above approximately 40° C.
PCB1: Power supply board: power supply unit for charging of batteries and capacitors, protected by CB1

PCB2: Switch unit driver (SUD): controls the magnetic actuator with monitoring of end positions, monitoring for broken cable and
with discharge switch for the capacitors PCB3: Capacitors for magnetic actuator

1 Arrangement of PCB1, PCB2 and PCB3 may vary based on
order-specific requirements. For actual arrangement, see
order-specific drawings included with each control cabinet.
Discharge switch for the capacitors The discharge toggle switch on the switch unit driver (SUD) module/printed circuit
board PCB2 serves to discharge the capacitors. In the "discharge capacitors" position (right position), the capacitor charging operation is turned off and the capacitor discharged via a resistor –
discharge of the capacitors takes roughly one minute.
In the "operating" position (left position), as shown in Figure 15, the red discharge LED next to the switch shows the voltage
at the capacitor is more than 40 V (LED on). Work on the capacitor should only be performed once the LED no longer
illuminates. For normal operation, the switch must be brought into the "operating" position (left position) – however, the LED does not light up during operation.

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