Description: 

This application note is providing information for a Dual Mutual Standby application using AMF compact controllers of CRE Technology.

 The Dual Mutual Standby is an application with 2 generators in Auto Mains Failure of 1 single mains connection.

Both generators will ensure mains failure detection but only 1 at the time will start and change over if requested ; the secondary genset is in standby and will take over the backup sequence if the primary fails, or if customer sequence is requesting to switch priority from primary to secondary genset.

Dual Mutual Standby exists in two different configurations:

Mode 1: Installation with separate GE and network source inversion:

 

Mode 2:  Dual Transfer switch with redundant mains monitoring.:

In both cases:

The generators cannot be in parallel and cannot be started at the same time, meaning they are backup for each other. There is a priority on the generators, so the customer can select the main backup generator based on a logic input, fault, or defined time period.

- When the mains fails, one generator provides backup, and in case of failure of this generator, the second generator takes over managing the mains loss.

- All circuit breakers or ATS in the installation are interlocked (mechanical interlocking is strongly recommended in addition to the application note).

Hardware requirement:

1. Two x AMF Compact A56-AMF (Core or HMI)
2. Ethernet cable RJ45 CAT5e max
3. Recommended: Ethernet industrial switch NITE-RS8-1100 (8 port) or 22496 (5 port).

Installation:

Mode 1: Installation with separated Gensets transfer switch and network transfer switch

To ensure reliable and responsive Dual Mutual Standby functionality between the AMF controllers, it is mandatory to establish an Ethernet connection via an RJ45 cable between the two controllers; communication can be direct, but we recommend installing an additional switch.

Mains (utility) side control:

- Both AMF Compact devices will be installed identically on the mains side, meaning they will both individually monitor the voltage and current (if applicable) of the mains.

- Both AMF devices will provide the same command to close the mains breaker ("I" position order), and the mains breaker position feedback must be inhibited (do not wire it to the AMF and do not declare the position on digital inputs).

The transfer switch mains position command of each AMF will thus be wired in parallel to the mains position order ("I" position).

- The command for the GEN position (backup) of the tranfer switch will be either request by the NO of the mains breaker position command, or by wiring the "Mains breaker open" commands of each AMF in series on the GE position (backup or "II" position) of the transfer switch.

GEN side control:

- AMF 1 will provide via its "GE breaker close" command the request to close the GE1 side of the GEN transfer switch.

- AMF 2 will provide via its "GE breaker close" command the request to close the GE2- side of the GEN transfer switch.

The GE position feedback of each AMF can be wired.

This wiring recommendation will ensure control redundancy in case of failure not only of a generator but also of the entire control system (including the AMF controller).

Each AMF will control its own generator, as is the case in typical AMF installations. 

Simplified wiring diagram:

Configuration:

Files and adresses:

You will find attached standard configuration files "Dual Mutual Standy - Mode 1" to download in both AMF controllers prior to start configuration, the configuration file is including Dual Mutual Standby features as explained in this application note.

There is 1 file for primary genset and 1 file for secondary genset.

Once file is downloaded in both controllers, you can configure the controllers normally (settings of nomnial values, I/O configuration, protections, ...)

Note: the dual Mutual standby is using standard IP adresses:

•     192.168.11.2 for AMF GEN 1
•     192.168.11.4 for AMF GEN 2

In case different IP addresses are used, just change the requested IP adresses in the following menus: Configuration/System/Nework, and Configuration/Programming/Modbus/Modbus Server (the IP here should be the IP of the other AMF).

Automatic priority changing:

In Automatic operation, Primary AMF (GEN 1) is always starting in priority in case of start request (Mains failure, remote start, TEST mode...), the Secondary AMF (GEN 2) will take over the sequence of AMF 1 and start GEN 2 in the following cases:

• GEN 1 is faulty and its Genset Circuit Breaker is opened.
• AMF of GEN 1 is not responding on the communication (Ethernet communcation failure or AMF 1 powered off.

As long as Primary AMF (GEN 1) is out of service, secondary AMF (GEN 2) will keep control and monitoring of the mains side.

Cycles of priority changing:

It is possible to change automatically the priority of the genset from Primary to Secondary.

The default cycles is changing every 6h starting from 00:00, this daily cycle is the minimum value, it can be changed to longer cycles (ex: every 2 days, every week, every month...).

To change priority just select requested cycle in Scheduler menu: Configuration/Programming/Scheduler/"saved var.1 - Dual Mutual Stdby Cycle.

Notes:

The secondary AMF is not monitoring the mains power and won't display mains voltage, but it is still possible to start/stop and close genset circuit breaker manually on the secondary genset for test purposes, make sure the interlock between both GCBs is effective, and primary genset is off before operating the secondary genset in manual.

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Mode 2: Dual Transfer switch with redundant mains monitoring.

In this case, the 2 AMFs will each control a source inverter, so it will be easier to manage the configuration as each is independent of the other. Installing an RJ45 cable between the two controllers is essential for cyclic rotation and system security.

Each AMF will control its own generator set, as is the case in usual AMF installations.

Simplified wiring diagram :

Configuration :

Files and addresses:

Attached are the standard configuration files "Dual Mutal Standby - Mode 2" to be downloaded into the two AMF controllers before starting the configuration, the configuration file includes the ‘Dual Mutual Standby’ functions as explained in this application note.

There is one file for the main genset and one file for the secondary genset.

Once the file has been downloaded to both controllers, you can configure the controllers as normal (nominal value settings, I/O configuration, protections, etc.).

Note: Dual Mutual Standby uses standard IP addresses:

192.168.11.2 for AMF GEN 1
192.168.11.4 for AMF GEN 2

If different IP addresses are used, simply change the IP addresses requested in the following menus: Configuration/System/Network, and Configuration/Programming/Modbus/Modbus Server (the IP here must be the IP of the other AMF).

Automatic priority change :

In automatic operation, the primary AMF (GEN 1) always starts with priority in the event of a start request (mains loss, remote start, TEST mode, etc.). The secondary AMF (GEN 2) takes priority and will start GEN 2 automatically when required in the following cases:

- AMF 1 has a serious fault
- Logic input 5 "AMF 2 Priority" is active on AMF 2.

As long as the primary AMF (GEN 1) is out of service, the secondary AMF (GEN 2) controls and monitors the network side.

When AMF 1 returns to normal conditions, or logic input 5 "AMF 1 Priority" is active on it, AMF 1 again takes priority.

Cyclic rotation:

This operating mode does not include cyclic rotation by default, however it is possible to implement this function by associating the "AMF n Priority" input function with the scheduler function, taking care to define consistent cycles for the AMFs.



End of procedure