Owen Brothers Metering can supply any DIN-Rail or Panel Mounted meter within our range in quality sealable metering panels also known as Meter Management Units or MMU’s that provide quick, easy and safe installation of CT operated devices.
Our IP rated metering panels include as standard DIN rail Fuses (Including spare fuse within each carrier), Earth and Neutral disconnect terminals with options such as Test Terminal Block (TTB) or CT shorting block assemblies for safe, accurate and legal installations.
CT Operated Meters are used extensively for measuring current and monitoring the operation of the power grid. Along with voltage leads, revenue-grade CTs drive the electrical utility's watt-hour meter on virtually every building with three-phase service and single-phase services greater than 100 amps. The CT is typically described by its current ratio from primary to secondary. Often, multiple CTs are installed as a "stack" for various uses. For example, protection devices and revenue metering may use separate CTs to provide isolation between metering and protection circuits, and allows current transformers with different characteristics (accuracy, overload performance) to be used for the devices.
Care must be taken that the secondary of a current transformer is not disconnected from its load while current is in the primary, as the transformer secondary will attempt to continue driving current across the effectively infinite impedance up to its core saturation voltage. This may produce a high voltage across the open secondary into the range of several kilovolts, causing arcing, compromising operator and equipment safety, or permanently affecting the accuracy of the transformer.
To avoid personal injury or equipment damage, the secondary must always be short-circuited or connected to a burden.
A solution for this problem is installation of our Test Terminal Block (TTB) that allows for safe testing, disconnection of the equipment leaving CT’s securly short-circuited.
Using our test/disconnect terminals also reduces possibility of damage to Current Transformers.