Use-cases of the Greenwood-Power sensors #3

Switch condition monitoring and detection

A simple and basic use case for sensors are the recognition of the switch state of load- switches and circuit breakers or the status of fuses.

Utility companies have more and more possibilities to control the substation switching via telecontrol units but have no response about the switching or state of a feeder.

For this use case already many Ring-Main-Units are equipped either with a capacitive tap on the bushing of a gas insulated switchgear or as dedicated capacitive support type insulator in air insulated switchgears. On the primary energy distribution, the C-Tap is integrated in conventional instrument transformers.

The technology behind this product is a capacitive voltage divider, which is connected to one of following systems:

• HR- High resistance… Input impedance of the device 36MΩ
• LR- Low resistance… Input impedance of the device 2MΩ
• LRM- Low resistance, modified… Input impedance of the device 2MΩ

The lack of information from the grid, needs to install more voltage detection points, doesn´t matter if the c-tap from bushing is used, or a cone type detector (GIS), a support insulator detector (AIS) or and Outdoor solution is used.

If there is a system installed, it needs a second step to bring the information to the data processor. This means, the system must have an interface to transmit the data to a local RTU. Most of the systems are pure indication systems with a display or indication lamp, which have the purpose to show the technician in front of the switchgear, if there are dangerous voltages or not.

GWP have developed a substitute of their products, to offer all products as detection systems.
The technology inside is a pure capacitive divider with an output adjusted to a capacitive measurement system. The biggest advantage is a high cost efficiency due to the lower technical demands and simpler structure.