Table of Contents
Do I need a CT meter?
Current Transformer (CT) Metering is a requirement for supplies with an anticipated load of over 100Amp/ 70kVA. Anyone installing or refurbishing power supplies rated >100Amp/ 70kVA will need to incorporate CT metering in their design.
What is the difference between whole current meter and CT meter?
A whole current meter is where the electricity supply passes through the meter itself, while a current transformer (in simple terms an electro-magnetic ring around the wire) or CT meter is where current transformers are used.
What is a CT connection?
CT (Current Transformer) Meters are installed on any connections with a load greater than 100 Amps. Conventional meters cannot be used to measure current for these larger connections as they would simply have to be too large to be practicable.
How do you attach a meter to a CT?
Key Points
- Install CTs on the phase conductor that corresponds to the voltage input phase.
- Install CTs with the arrow or label ‘This side toward source’ facing towards the breaker feeding the load.
- Connect the white and black CT leads to the corresponding CT input terminals with the white and black dots.
What is a CT supply?
A CT Chamber houses current transformers for low voltage metering applications. When the supply to a site needs to be greater than 100 A (~70 kVA at 415 V) then the electricity meter works with current transformers (CTs) housed within their own enclosure – the CT chamber.
How do I connect to CT?
Why CT secondary is shorted?
A CT has generally 1:1000 or 1:2000 primary:secondary ratio. Now if secondary of CT is left open then a extremely high voltage will appear across open secondary ends which might damage CT. Therefore secondary is intentionally shorted when output is not connected to any measuring instrument.
Can you splice CT wires?
Splicing. When the 8 foot lead wires on standard stock CTs are not long enough, you can extend them by splicing on additional wire. Avoid creating large loops or gaps between the white and black wires at the junction point, because this can increase electrical interference.
What is a CT meter and how does it work?
A CT meter is simply a meter that is used in conjunction with instrument transformers known as current transformers. These are also known as CTs. In electrical metering, meters are divided into two types.
How does an electricity meter work?
Electricity meters… are either ‘whole current’ (direct connect), where all the electricity flows through the meter, or CT meters, where the electricity flows through a Current Transformer which reduces the electricity to flow through the meter by a defined ratio.
Can a 3 phase meter be a whole current meter?
Technically it is easy to make a 3 phase “whole current” meter. My interpretation onlyis that a shunt based meter would be whole current if you used “ohmic connections” to measure the drop across the shunt but probably not if you used eg a Hall sensor to measure current in the shunt.
What is the CT and PT ratio of a meter?
Some typical PT’s are 2.4:1 and 4:1. Now that we know what CT’s and PT’s are, we can talk about meter multipliers. Meter multipliers are used when meters are installed in transformer-rated installations. If the CT ratio is 200:5, then the meter multiplier is 40, which is simply 200/5.