Metering Units & Capacitive Bushing Insulators
The whole revenue metering point, ordered as one assembly.
At the point of delivery the utility does not measure current and voltage separately. It measures energy, and everything in that measurement chain has to agree. A metering unit puts the current transformer and the voltage transformer in one outdoor-rated assembly, factory built and factory tested together, so the ratio, the burden and the terminal arrangement stop being three separate purchase decisions that meet for the first time on the pole.
The range covers 15 kV, 25 kV and 36 kV classes at 60 Hz, with capacitive bushing insulators in the same three classes, and indoor metering pole assemblies with or without fuse provision. Instrument transformer accuracy follows IEEE C57.13, with IEC 61869-2 and 61869-3 designations available for projects written to IEC.
Why it matters
One assembly instead of two instrument transformers plus a mounting design removes the field fabrication step where most metering installations lose time.
Outdoor rating across 15, 25 and 36 kV classes covers the point-of-delivery installations that sit on a pole or a structure rather than inside a building.
Capacitive bushing insulators in matching classes give a defined capacitive tap, which is what an online bushing or PD monitor later connects to.
Indoor metering poles with or without fuse provision cover the primary metering cabinet without a separate fuse mounting design.
IEEE C57.13 accuracy on both the current and voltage elements keeps the whole unit inside one billing accuracy argument.
Ratings
Metering units: Combined CT + VT assemblies for 15 kV, 25 kV and 36 kV classes, outdoor rated
Capacitive bushing insulators: 15 kV, 25 kV and 36 kV classes
Metering poles: Indoor metering pole assemblies with and without fuse provision
Frequency: 60 Hz
Standards
IEEE C57.13
IEC 61869-2/-3
ABNT NBR 6855 / 6856
Applications
Utility revenue metering at the point of delivery
Primary metering cabinets
Consumer entrance substations
Cross-border and interchange metering
Questions engineers ask
What is a metering unit and when is one specified instead of separate CTs and VTs? A metering unit is a combined current and voltage transformer assembly in a single outdoor-rated housing, used at the point of delivery. It is specified when the utility requires a factory-built, factory-tested metering point rather than instrument transformers mounted separately in the field. It shortens installation and keeps the accuracy argument to one device.
What is a capacitive bushing insulator used for? A capacitive bushing insulator carries the conductor through a grounded barrier and provides a capacitive tap referenced to the internal grading layers. That tap is the connection point for voltage sensing and for online bushing capacitance, dissipation factor and partial discharge monitoring. Units are offered in 15, 25 and 36 kV classes.
