Testing of CT Burden
- Thread starter praichura
- Start date
Gil47
Member
With great caution
NEVER open circuit the secondary of a CT when any current is flowing in the primary.
As high voltages can occur which can cause serious injury or consequences.
It could be a case, that if you need to ask, then you need personal instruction,
and personal guidance while these tests are performed.
Using Ohms law
The CT has a given output current
A given VA rating
Driving a resistive load where you can derive and also measure a voltage
NEVER open circuit the secondary of a CT when any current is flowing in the primary.
As high voltages can occur which can cause serious injury or consequences.
It could be a case, that if you need to ask, then you need personal instruction,
and personal guidance while these tests are performed.
Using Ohms law
The CT has a given output current
A given VA rating
Driving a resistive load where you can derive and also measure a voltage
Last edited:
Jim Dungar
Member
The burden a CT can handle is determined by the saturation curve of its core. You can not determine saturation by simple resistance tests.
The easiest way to determine burden is to look up the specifications of the CT.
If you cannot do that then you can make some estimates by comparing its physical size and weight with other similar units that do have known burdens. CT's that can handle large burdens are heavier than small burden units.
The easiest way to determine burden is to look up the specifications of the CT.
If you cannot do that then you can make some estimates by comparing its physical size and weight with other similar units that do have known burdens. CT's that can handle large burdens are heavier than small burden units.
First of all thanks for ur reply Jim.
why we need to check the CT burden is that our clients & contractors are asking us that the same VA CT we are getting at the cheaper price. I know that many companies are just writing VA as they like, though we are convincing the clients by physical estimation only. If other way is possible we can definately prove dat
why we need to check the CT burden is that our clients & contractors are asking us that the same VA CT we are getting at the cheaper price. I know that many companies are just writing VA as they like, though we are convincing the clients by physical estimation only. If other way is possible we can definately prove dat
Jim Dungar
Member
The manufacturer should be able to supply a saturation curve. If they can not the CT is probably not rated for a very high burden.
leitmotif
Member
Jim
teach me something. As an example in a mag amp or arc welder with additional winding (DC) the transformer core is partially saturated to control output.
QUESTION
with a CT (0r any other transformer for that matter) IF the unit is operating at design values ie current ratio in a CT then you would not need to worry about saturation. Now if you overload it then maybe you would need to worry about saturation (for instance CTs in a motor starter) - am I right?
Dan Bentler
teach me something. As an example in a mag amp or arc welder with additional winding (DC) the transformer core is partially saturated to control output.
QUESTION
with a CT (0r any other transformer for that matter) IF the unit is operating at design values ie current ratio in a CT then you would not need to worry about saturation. Now if you overload it then maybe you would need to worry about saturation (for instance CTs in a motor starter) - am I right?
Dan Bentler
yes for that purpose only the burden will count? at the time of the designing you have to select the suitable burden for it, according to ur requirement either u have to take it to the far place or the no. of instruments installed are how much? whats the burden of the instruments used, these all matter should be considered & also wire esistance should be considered if u have to take the value at some remote place.
Jim Dungar
Member
CT's get overloaded all of the time. Saturation is not an issue for metering purposes but it is for protective relaying.
Say you have a CT providing over current protection to a motor. The normal operating range of the CT is probably a maximum of 2 times the FLA of the motor, but its normal overload trip is in the area of 6x for 10-20sec. Then it needs to be able to have a proportional output during the motor startup period which requires maybe 8-10 times FLA for may 1-5 sec. And then the CT must be able to indicate a short circuit which may be 20-30 times FLA instantaneously.
leitmotif
Member
Jim
Thanks. I worked briefly with a couple meter and relay engineers while at Trojan. So the message for CTs is about the same as that for any equipment - identify the demands of load and your wants and size equipment for that.
Thanks
Dan Bentler
Thanks. I worked briefly with a couple meter and relay engineers while at Trojan. So the message for CTs is about the same as that for any equipment - identify the demands of load and your wants and size equipment for that.
Thanks
Dan Bentler
Similar Topics
I am working on setting up a Prosoft Datalogger model PLX51-DLplus-232. This unit will be collecting data from a SLC 5/05 on the DB9 port set to...
Hi all,
I have a AC current transducer that I want to bench test to ensure I am getting a 4-20mA output. I am using a AE001 unit. It is very...
Hi Guys,
Can ControlLogix with Modsim32 for Modbus Server Testing?
I have ControlLogix via Anybus Modbus TCP and I need to Test the...
Hello all, looking for ideas on getting some basic training done, I need to practice on maintenance timers and bypass switches (with a Factory...
I have a project in FTV ME (Studio v13) that I'm trying to apply security to a few buttons/setpoints.
I have 4 users: Anonymous Logon, DEFAULT...