Auto Load Transfer Scheme using the NMS 100

As well as providing remote control of pad/ground mounted switches and over head motor operators the NMS 100 has been used extensively to provide Auto Load Transfer for certain types of network configuration.

The ALT function in the NMS 100 is designed to allow an automatic operation of a set of switches to offer an alternative supply on loss of the primary supply. This could be used to protect key customers such as schools and colleges, hospitals, or critical infrastructure such as rail crossings, intersection lights etc.

• In the example above the NMS 100 with Auto Load Transfer (ALT) function at the substation is controlling two NME motor operators. It could also be controlling motor controlled pad mounted switches, or vacuum circuit breakers.
  

• One of the NME motor operators is in the open position and there is a VT on the supply side of each to monitor the  HV.
  

• When a loss of voltage is detected at the substation. The incoming switch will open and the normally open point will close. This can be further complimented with Fault Current Detection, so that if loss of volts is detected along with fault current, the unit will not witch to the alternative supply.
  

• The Auto Load Transfer functions independently of the central network, but commands from a CCU or from the Network Management Centre will override automation in the ALT switch. There is also a facility to switch the function in and out from the control panel. Furthermore loss of voltage at both switches prevents the scheme from operating and any remote control of the switches will instantly disarm the function.