Licht MFC-300/P User manual

Parallelism Controller
model MFC-300/P
Technical Manual
Licht

Rev. A3 (29–05–12) MFC-300/P Technical Manual 1
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 Operating principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 Front panel indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2 Manual commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.4 Parameter reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4 Programmable parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1 MODBUS protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2 DNP3 protocol (option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5 Error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1 Synchronism error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.2 Position deviation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.3 Configuration error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.4 Communication error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
A Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
B Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
C Connection diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
D Configuration sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
E MODBUS registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

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Rev. A3 (29–05–12) MFC-300/P Technical Manual 2
1 Introduction
The MFC-300/P controller was developed by Licht for the paralellism supervision and
control of 3-phase power transformers and 3-phase groups of monophase transformers.
The MFC-300/P features 10 relays for electromechanic logic, one RS485 interface for
supervision and control and one optional current output for position retransmission.
The parallelism control is implemented according to the master-follower principle, under
which all tap changer positions are kept synchronized. For parallel control to be success-
ful under this scenario, we admit that all involved transformers have identical nominal
currents, number of taps and voltage delta per tap. Each tap changer’s position is read
directly from its potentiometric sensor or indirectly either via a current loop (typically 4-
20 mA) or BCD contacts, according to the client’s specifications. During parallel control,
the Master tap changer’s position is compared to its Followers’, and tap changer pulses
are issued to the Follower tap changers whose positions don’t match their Master’s.
In the MFC-300/P architecture, each controller is responsible for a 3-phase transformer
or a monophase transformer, and is interconnected with other MFC-300/P using a RS485
bus arrangement. MODBUS or DNP3 functionality is provided on a second dedicated
RS485 port, which does not require additional hardware.
Figure 1.1 MFC-300/P controller

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Rev. A3 (29–05–12) MFC-300/P Technical Manual 3
2 Operating principle
General Case
The operation of transformers in parallel can be motivated by expansion, redundancy or
convenience. For it to be practical, the transformers involved must have their secondary
voltages as similar as possible at all times. Otherwise, transformers with lower outputs
become loads to the others, creating circulation currents.
The MFC-300/P is designed for power transformers with on-load tap changers. These
can adjust their tranformation relation as their loads change, guaranteeing adequate reg-
ulation. The Master-Follower principle supposes that the involved transformers have tap
changers with the same number of taps, and that each tap corresponds to the same out-
put voltage. Circulation currents are minimized by operating transformers on identical
positions.
In the Master-Follower principle, a transformer which we denote the Master is chosen as
the reference. The others, denoted Followers, have their positions automatically updated
in order to match the Master. Parallel control is synchronous, because all transformers –
irrespective of being the Master or the Follower – receive simultaneous commands. Trans-
formers can be removed from parallel control if configured as Individual, and completely
ignored if configured as Disabled.
Some exceptional scenarios are detected and treated. These can vary from tap changer
failures (for example, when a Follower transformer doesn’t respond to commands and fails
to match its Master) to configuration errors (for example, configuring a Master without
Followers or Followers without a Master).
Master
Transformer
Position 9
Follower
Transformer
Position 9
Individual
Transformer
Position 5
Figure 2.1 3-phase Transformer Parallelism

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Rev. A3 (29–05–12) MFC-300/P Technical Manual 4
Manual Commands
Transformers configured as Master or Individual can be manually commanded by an
operator. This command may be local (issued on the controller’s keyboard) or remote
(with digital dry contact inputs).
If a Follower transformer fails to respond to tap change commands, the MFC-300/P will
ignore subsequent commands and signal the error condition. In this scenario, the oper-
ator must reconfigure the transformer as Individual and manually manage the system’s
parallelism until a solution can be found.

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Rev. A3 (29–05–12) MFC-300/P Technical Manual 5
3 Operation
3.1 Front panel indication
Under normal operation, the MFC-300/P indicates its channel’s position, operation mode
(Master, Follower, Individual, Disabled) and, if applicable, the raise (↑) or lower (↓)
command indications. Figure 3.1 presents a front panel indication example.
R3
R4
R5
R1 command
manual
master
follower
R6
R7
individual
error 1
R8 error 2
R9 error 3
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MULTI FUNCTION CONTROLLER
MFC-300/P
C
P
Mode: Individual
Pos 01 Addr01
R3 R4 R5 R6
R1 R2 R7 R8 R9
R2 command
Figure 3.1 Front Panel
In alarm situations, the display alternates between an error message and the channel’s
indication, regardless of the device’s configuration.
3.2 Manual commands
Transformers configured as Master or Individual can be directly commanded by the MFC-
300/P with a manual command. Whenever the transformer is configured as Follower or
Disabled, the command is ignored. Manual commands are only accepted if there’s no
synchronism error between all tap changers.
To perform a manual command, press P, choose the “Manual Command” option, press
Pagain to confirm and then issue a raise or lower command with the ↑or ↓key.
Master
Transformer
↑Position 7 ↑
Follower
Transformer
Position 7
Individual
Transformer
Position 4
Figure 3.2 Raise Command Example (Before)
3.3 Configuration
The MFC-300/P features 4 keys to access its functions. The procedure to configure any
parameter is as follows:

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Rev. A3 (29–05–12) MFC-300/P Technical Manual 6
Master
Transformer
Position 8
Follower
Transformer
Position 8
Follower
Transformer
Position 4
Figure 3.3 Raise Command Example (After)
1. Press the Pkey to enter the parameters menu.
2. Using the ↑and ↓keys, choose the desired parameter.
3. Press Pto confirm the parameter’s selection.
4. Choose the desired value with the ↑and ↓keys.
5. Confirm pressing P.
The configuration sequence can be cancelled at any time by pressing C.
3.4 Parameter reset
The MFC-300/P can be reset to factory settings. This procedure also resets its password
to AAAA. To do so, power on the device while pressing C.

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Rev. A3 (29–05–12) MFC-300/P Technical Manual 7
4 Programmable parameters
The MFC-300/P was developed to provide the user with the greatest possible flexiblity,
such that all supervision and configuration can be executed on-site or remotely through
the existing communication channels.
We define all user-configurable parameters as follows:
Parallelism Mode1
Options:Master,Follower,Individual or Disabled
Description: Selects if the channel operates as Master, Follower, Individual or Disabled.
Number of Positions
Options:2to 50
Description: The on-load tap changer’s number of positions.
Resistance per Position
Opções:3to 20 Ω
Descrição: Resistance in Ωper tap changer position.
Synchronism Error Timeout
Options:10 to 100 s
Description: Interval defined from the instant when failure to follow was detected to
this error’s indication.
Configuration Error Timeout
Options:10 to 100 s
Description: Interval defined from the instant when a configuration failure was detected
to this error’s indication.
Address
Options:0 to 15
Description: Configures this MFC-300/P’s network address. Each tap changer must
have a unique address. A network of MFC-300/Ps can control up to 16 transformers.
Output Current (if any)
Options:0-1,0-5,0-10,0-20,4-20 mA
Description: Refers to the various configurable current loop scales.
This parameter can be only configured using dry contacts.
1

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Relay {7, 8, 9}Configuration
Options: Refer to the table below.
Description: Defines the activation condition for programmable relays 7, 8 e 9.
Activation Condition Occurrence Site Default State MODBUS
Value
Synchronism Error Any MFC-300/P FC 0
FO 1
Configuration Error Any MFC-300/P FC 2
FO 3
Communication Error Any MFC-300/P FC 4
FO 5
Position Deviation Any MFC-300/P FC 6
FO 7
Normal Operation Any MFC-300/P NC 8
NA 9
FC: fail closed
FO: fail open
NC: normally closed
NO: normally open
4.1 MODBUS protocol
Parameter:Baud Rate
Options: 9600, 19200, 38400, 57600, 115200 bps.
Description: baud rate for the RS485 link.
Parameter:Format
Options: 8N1, 8E1, 8O1, 8N2.
Description: symbol transmission format, where:
◦8N1: 8 data bits, no parity, 1 stop bit.
◦8E1: 8 data bits, even parity, 1 stop bit.
◦8O1: 8 data bits, odd parity, 1 stop bit.
◦8N2: 8 data bits, no parity, 2 stop bits.
Parameter:Address
Options: 1 to 247.
Description: MODBUS address for the MFC-300/P.

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4.2 DNP3 protocol (option)
Parameter:Baud Rate
Options: 9600, 19200, 38400, 57600, 115200 bps.
Description: baud rate for the RS-485 link.
Parameter:Format
Options: 8N1, 8E1, 8O1, 8N2.
Description: symbol transmission format, where:
◦8N1: 8 data bits, no parity, 1 stop bit.
◦8E1: 8 data bits, even parity, 1 stop bit.
◦8O1: 8 data bits, odd parity, 1 stop bit.
◦8N2: 8 data bits, no parity, 2 stop bits.
Parameter:Address
Options: 0x0000 to 0xFFEF.
Description: DNP3 outstation address in hexadecimal notation.
Parameter:Application Layer Confirmation
Options: Only when transmitting events or multi-fragment responses, Always.
Description: Selects when the MFC-300/P outstation should request application layer
confirmations.
Parameter:Maximum Inter-Octet Gap
Options: 2 to 100 ms.
Description: The DNP3 specification states that frames should not have inter-octet gaps.
In accordance, the MFC-300/P never inserts inter-octet gaps when transmitting data.
However, we allow the option to tolerate gaps in incoming transmissions. Frames featuring
inter-octet gaps larger than the Maximum Inter-Octet Gap will be quietly dropped.
Parameter:Backoff Delay (Fixed)
Options: 1 to 100 ms.
Description: See description for Backoff Delay (Random).
Parameter:Backoff Delay (Random)
Options: 1 to 100 ms.
Description: The MFC-300/P is designed for multi-drop scenarios where more than
one outstation may transmit over the same line. To handle collision avoidance, a backoff