What Is CT Metering?
A plain-language explanation of CT metering — how current transformers work, when CT metering is required and how it differs from direct-connect metering.
Metering big loads safely
CT metering uses current transformers (CTs) to scale the load current down to a small, safe level that the meter can measure. This means the meter never has to carry the full current, which makes it possible to meter large commercial and industrial services where the current is far too high for a direct-connect meter.
CT versus direct connect
The measurement method depends on the size of the load.
| Method | How it works | Typical use |
|---|---|---|
| Direct connect | Full current through the meter | Residential, small commercial |
| CT metering | CTs scale current for the meter | Large commercial, industrial |
When it's required
The changeover to CT metering is set by the network's rules for the service capacity. Once the current exceeds what a direct-connect meter can safely carry, CT metering is required — which changes the panel, the enclosure and the wiring. EVO fabricates CT metering panels and switchboards for the trade; request a quote with your service details.
Frequently Asked Questions
When is CT metering needed instead of direct connect?
When the load current exceeds what a direct-connect meter can safely carry, as set by the network's rules for the service capacity — typically on large commercial and industrial services.
What is a current transformer?
A current transformer scales the load current down to a small, safe level the meter can measure, so the meter never carries the full current of a large service.
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Keep Reading
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A trade reference on multi-tenancy metering — metering panels for units and dual occupancies, CT metering, labelling, segregation and how to specify a multi-meter installation.
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How to pick between 300x300, 400x400, 500x500, 600x600 and 600x900 meter boxes for residential and commercial metering installations.
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