Woodward MRA1 User manual

MRA1 –Trip Circuit Supervision
Manual MRA1 (Revision C)

Woodward Manual MRA1
2 DOK-TD-MRA1 Rev. C
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© Woodward 1994–2019

Manual MRA1 Woodward
DOK-TD-MRA1 Rev. C 3
Contents
1. Introduction and application.......................................................................4
2. Features and characteristics ......................................................................4
3. Design...........................................................................................................5
3.1 Connections ........................................................................................................................5
3.2 Coding plug.........................................................................................................................6
3.3 Coding of the LED function .................................................................................................7
3.4 Coding Auto/Manual Reset.................................................................................................8
4. Functions......................................................................................................9
4.1 Supervision of the voltage supply of the protection devices...............................................9
4.2 Cable break supervision......................................................................................................9
4.3 Front plate.........................................................................................................................10
4.4 LEDs..................................................................................................................................11
4.5 Status indicator..................................................................................................................11
4.6 Resetting...........................................................................................................................11
4.7 Terminal block...................................................................................................................12
5. Testing the relay and commissioning......................................................14
5.1 Connecting the auxiliary voltage.......................................................................................14
5.2 Testing the supervision circuits.........................................................................................14
5.3 Testing the AUTO-RESET function ..................................................................................15
5.4 Testing the external RESET inputs...................................................................................15
5.5 Testing the LED function...................................................................................................15
6. Technical Data............................................................................................16
7. Order form..................................................................................................18

Woodward Manual MRA1
4 DOK-TD-MRA1 Rev. C
1.Introduction and application
The MRA1 - relay of the HIGH TECH LINE is used to supervise the tripping circuit of protective de-
vices taking into consideration the following protective criteria:
supervision of the auxiliary voltage for the tripping circuit and for the supply of protective
devices
supervision of the tripping circuit with regard to cable break
supervision of the mechanical functions of the circuit breaker
2.Features and characteristics
high breaking capacity of the relay contacts
in compliance with the requirements as per BS 142 and IEC 255
manual/automatic reset
coil resistance of tripping coil may be up to 12 k
supervision independent of the circuit breaker position
wide range power supply for all nominal supply voltages

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3.Design
3.1 Connections
Figure 3.1: Connection diagram MRA1 Version "A" Application with opener and shutter contacts of the circuit breaker
Figure 3.2: Connection diagram MRA1 Version "B" Trip supervision with a shutter contact

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3.2 Coding plug
Switching thresholds of the input circuitry
The MRA1 has a wide-range power pack for all commonly used voltage values. For this reason the
pick-up thresh-olds of the internal relays K1, K2, K3 and the reset input must be adjusted to the
existing rated voltage.
There are 4 switching thresholds available which can each be changed by 2 coding plugs.
Switching threshold
Coding plug A
Coding plug B
9V
plugged
plugged
30V
Not plugged
plugged
65V
plugged
Not plugged
100V
Not plugged
Not plugged
This means that each input can be switched separately. (Refer to set-ting lists on last page)
The coding plugs are located inside the device on the bottom side of the relay card.
Figure 3.3: Coding of the pick-up thresholds of the internal relays K1, K2, K3 and the reset function

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3.3 Coding of the LED function
The MRA1 can be used for two different monitoring concepts.
a) Supervision of the circuit breaker by two supervision circuits. The opener and the shutter
contacts of the circuit breaker are supervised separately. (P = parallel connection)
b) Supervision of the circuit breakers by one supervision circuit (S=serial connection)
For this reason the switch position indication, which is shown by LEDs on the front plate of the
MRA1, must be coded.
In circuit version "A" the coding plug must be in position "P" and for the circuit version "B" it must be
in position "S".
The coding plugs are located inside the device on the bottom side of the relay card.
Figure 3.4: Coding plug MRA1 LED function

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3.4 Coding Auto/Manual Reset
Behind the front plate of the MRA1, on the bottom side, there is a coding plug for pre-setting the
reset behavior of the output relay.
If the coding plug is plugged in, the output relay and the indicator are set back if the fault, e.g. line
break, has been corrected.
If the coding plug is not plugged in, the output relays and the must be reset manually by activating
the reset key or the external reset function.
Figure 3.5: Position of coding plugs

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4.Functions
4.1 Supervision of the voltage supply of the protection devices
Relay K1 is released if the voltage drops below the voltage pre-set with the coding plugs (refer to
Chapter 3.2).The relay is energized in steps of 5 V each above the release point of the coded
switch point. In order to bridge brief drops (up to approx. 200 ms), an RC circuit is connected in
parallel. The "OK" LED lights up green if the tripping circuit is free of faults.
Relay K1 is in pick-up condition if the entire tripping circuit is in order.
4.2 Cable break supervision
The MRA1 can be used for two different monitoring concepts.
a) Supervision of the circuit breaker by two supervision circuits. The opener and shutter
contacts of the circuit breaker are supervised separately. (P=parallel connection)
b) Supervision of the circuit breakers by one supervision circuit (S=serial connection).
Version "A": Depending on the position of the circuit breaker, K2 or K3 will be energized and thus
switch relay K1 on. The LEDs OK and CB OFF light up green. The LED CB ON lights up red. In
case of a cable break, the relevant relay (K2 or K3) and K1 are released.
Position of the circuit breaker:
Circuit breaker –OFF:
The aux. contact (opener) of the circuit breaker is closed and K3 is active.
In case of supply voltage failure, K1 is released and the relay trips.
If the tripping coil of the circuit breaker is interrupted, K3 is re-leased and consequently also K1,
and the relay trips.
Circuit breaker –ON:
K3 releases with delay.
K2 is energized undelayed via the aux. contact (shutter) of the circuit breaker and K1 remains ac-
tive.
Protection trips:
K2 release is delayed about 400 ms, which thus bridges the protection relay contact time-wise. If
the circuit breaker does not switch off despite the switch-off command, the contact of the protection
relay remains closed. After approx. 400ms K2 and K2 are released. The trip relay K1 is then in trip
position. (Refer Figure 3.1)
Version "B": With this With this version relays K2 and K3 are energized. In case of a cable break
K2 and K3 are released and subsequently also K1.
Position of the circuit breaker:
Circuit breaker –OFF:
Switch position indication only re-quires one shutter contact of the circuit breaker. If the circuit
breaker is switched off, K2 and K3 are active. In case of supply voltage failure K1 releases and the
relay trips.
If the trip coil of the circuit breaker is interrupted, K2 and K3 are released and consequently also
K1, and the relay trips.

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Circuit breaker –ON:
K3 is released with delay action by short-circuiting the circuit breaker by means of aux. contact
(shutter). K1 remains active as K2 remains energized.
Protection trips:
Tripping of the protection relay will bridge K2. On account of the release delay by 400 ms, the pro-
tection relay contact is bridged timewise. If the circuit breaker does not switch off despite switch-off
command, the con-tact of the protection relay remains closed. After approx. 400ms K2 and K1 will
be released. The trip relay K1 is then in release position. (Refer to Figure 3.2)
4.3 Front plate
Figure 4.1: Front plate MRA1