Current Transformer (CT) & Potential Transformer (PT) Testing
Instrument transformers play an important role in revenue calculation. One small error can lead to significant revenue loss for a utility district.
PowerMaster® site analyzers accurately test instrument transformer performance using the following test methodologies:
Ratio –
Customer load test consisting of direct simultaneous measurement of primary and secondary signals. Both amplitude and phase error measurements are verified and graphically plotted according to IEEE.
Ratio with Burden Added –
Customer load test consisting of direct simultaneous measurement of primary and secondary signals while adding additional burden to the CT circuit. Both amplitude and phase error measurements are verified and graphically plotted according to IEEE. Adding burden in this manner stresses the CT to determine at what point it will become over-burdened and inaccurate.
Burden Measurement –
Customer load test consisting of direct simultaneous measurement of the secondary current signal of the CT, and the voltage drop across its terminals. Accurately measuring these signals allows the calculation of the existing burden on the CT. This burden measurement is verified against the specification from the CT manufacturer.
Dead Site / Load Boost –
Generated load test consisting of direct simultaneous measurement of primary and secondary signals while injecting additional current to the primary of the CT. Both amplitude and phase error measurements are verified and graphically plotted according to IEEE.
Accuracy
Most metering class instrument CTs are rated at 0.3% accuracy within their burden and temperature specifications at full rated load. There is also a new, more accurate class of CTs which are rated at 0.15%.
Because of the importance of CTs in the billing chain, it is imperative that the test equipment used to verify their accuracy has proven accuracy much greater than the CTs.
Faulty installation and overburdening are just a few instances that will reduce the accuracy of the CT installation.
Powermetrix PowerMaster® solutions give you functionality, portability, and accuracy in the field for exact readings even when the most complex testing is necessary.
PowerMaster® site analyzers provide ease of use in a compact and feature-rich package. They’re built into a rugged Pelican hard case, enabling them to stand up to the rigorous demands of field testing.
7 Series – True three phase reference standard with optional three phase current and voltage sources for ANSI C12 phantom load meter testing. Customer load testing is readily performed on electric meters, CTs, PTs and transducers. You can add the MTA-15Z accessory to facilitate ANSI C12 meter testing on self-contained meters at the customer’s site or in the lab.
3 Series – Our most compact true three phase reference standard for testing meters under customer load conditions. It also enables the technician to test CTs and PTs, and with CAT IV 600V and IEC-61010 safety compliance, it protects them more than anything else in its class.