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BSC-50: Earth ground fault detection & alarming at medium voltage substations
Introduction Medium voltage substations require monitoring in order to help power grid operators re-establish power when network faults occur.
Identifying a substation that is out of power is time critical to minimise operations to link back power on the grid.
Modern substations are equipped with earth ground fault detection relays, which provide a digital contact when a fault in the substation occurs. The goal is to reduce drastically the total time without power. The normal procedure when an fault is detected is to send maintenance crew to visit a series of substations, identify the stations which have a fault status and report this back to the control center. Then operations to reroute power are made remotely or on a trial and error basis which damages the network infrastructure.
All the time a substation is off the grid an area is without power.
Requirements - Identify faults almost online and alarm via sms to a control center, - Minimise needed power rerouting operations - Identify operational faults from substation equipment, - Intruder security alarming,
Proposal
A BSC-50 ultra low power GSM alarming RTU is ideal for digital alarm event annunciation using SMS.
The proposed system consists of, a) Remote alarming units, BSC-50 devices which are installed to supervise the operation of local installations of medium voltage substations.
At each substation a special fault detection relay is installed that detects earth ground faults and provides a plain contact as an alarm in the event of a fault. When an earth ground fault is detected in a substation the result is that the substation is automatically taken off the power grid. Manual or remote operations are needed to place the substation back on the grid.
The BSC50 devices monitor faults and limits breach and transmit respective coded messages via SMS to a control center. Moreover BSC50s can be configured to transmit a health message in a scheduled manner to the control center to insure their operational status. At the control center a PC running 24/7 the monitoring software logs alarms, monitors and reports the operational status of the BSC50 devices.
Integration to existing SCADA systems or GIS applications is seamless via an OPC server
Furthermore as an extension utilising M2M functionality, SCOM-100 devices can be used at the control center in order to have an unmanned system.
In this case, at the control center, a mimic diagram showing the geographic location of the substations and BSC50 devices is installed. The mimic diagram has built in colored leds at each substation. The leds are cabled to an M2M (machine to machine) alarm receiver device which is an SCOM100 unit. The leds are connected to digital outputs on the SCOM100. When an alarm occurs at a BSC50 two messages are send, one at the control center monitoring station running the monitoring SW and one to the SCOM100 device to switch on a led at the mimic diagram. If the fault is rectified the led can be switched off via a manual operation of a switch on the mimic diagram (alarm acknowledgement and rectification).
This way users at the control center can, a) visualize the location of the faults, b) see the sequence of failing substations,
in order to perform remote operations (if this is possible in respect to the local substation automation), or to order maintenance crew to visit a specific point on the grid to reroute power and maintain power in the areas which had been taken off the grid.
For example a BSC-50 that alarms instantly and sends as health message every week will operate on one Lithium Thionyl D type 3.6V battery for more than 12 years.
Why BSC-50 - All-in-one cellular GPRS quad band solution - Ultra low power, can run for years on one D type battery - Real-time alarming - Easy to implement and maintain - Seamless connection to SCADA via OPC server - SMS alarms and M2M functionality
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