Instrument transformers are important high voltage electrical devices that isolate and transform currents or voltages from higher magnitudes to lower magnitudes to provide safety of an end user and to protect a measuring device being used, such as a current or voltage measuring bridge, ammeter, or voltmeter. High currents are transformed using a current transformer (CT) and high voltages are transformed using a voltage transformer (VT), otherwise known as a potential transformer (PT).
Haefely / Tettex has a long-standing tradition of providing highly accurate instrument transformer test systems used to precisely measure current/voltage ratio errors, phase displacement, and excitation. Performing these tests helps to diagnose problems due to poor manufacturing or shipping damages, or identify changes in an instrument transformer due to ageing of the insulation. Complete test systems are suitable for current transformer and voltage transformer testing according to the latest IEC and ANSI/IEEE standards. Individual components, such as measuring bridges or electronic burdens can be individually integrated into an existing current transformer or voltage transformer test system.
Available Instrument Transformer Test Equipment
Frequently Asked Questions
What is the purpose of instrument transformer testing?
Instrument transformer testing evaluates the accuracy, phase displacement, ratio error, and overall insulation health of Current Transformers (CTs) and Voltage/Potential Transformers (VTs/PTs). Because these components step down high electrical values to safe levels for meters and protective relays, accurate testing prevents billing errors, improper grid relay operations, and catastrophic insulation failures.
What specific hardware systems does HV TECHNOLOGIES provide for CT and VT analysis?
HV TECHNOLOGIES offers industry-leading, high-precision test sets manufactured by HAEFELY / Tettex, engineered to align with global metrology standards.
The primary specialized systems include:
✔️CITAS 2771: A dedicated Current Instrument Transformer Analyzing Set.
✔️VITAS 2772: A dedicated Voltage Instrument Transformer Analyzing Set.
✔️Current Comparators: Models up to 1,000 A (4761) and 5,000 A (4764)
✔️Programmable Burdens: Models 3691 (Current Burden) and 3695 (Voltage Burden) for simulating load conditions.
What international standards govern instrument transformer test configurations?
HV TECHNOLOGIES’s complete test systems and modular components are designed to perform verification and diagnostic routines in strict compliance with the latest IEC (e.g., IEC 61869 series) and ANSI/IEEE (e.g., IEEE C57.13) standards. This compliance ensures that metrological accuracy evaluations hold legal and industrial validity worldwide.
What are programmable electronic burdens, and why are they necessary during testing?
Programmable electronic burdens, like the Tettex 3691 and 3695, simulate the actual connected electrical load (impedance or admittance) that an instrument transformer encounters in the field. Testing CTs and VTs under variable burden states is critical to verifying that ratio errors and phase angle deviations stay within their specified accuracy classes during real-world grid load fluctuations.
How do current comparators and electronic voltage dividers enhance calibration setups?
Current comparators (such as models 4761, 4762, and 4764) and standard electronic voltage dividers (4861) act as high-precision laboratory references. By introducing an ultra-stable, highly accurate benchmark value into the test circuit, these devices allow instrument transformer analyzing sets to accurately measure minute differences in magnitude and phase angle.
Can HV TECHNOLOGIES components integrate into an existing testing bay framework?
Yes. HV TECHNOLOGIES specializes in both complete, turnkey transformer testing bays and modular retrofits. Individual equipment pieces—such as Tettex measuring bridges, standard transformers, or programmable electronic burdens—can be seamlessly integrated into existing test systems to upgrade accuracy or automate reporting data.
How can I request technical specifications or a quote for instrument transformer test equipment?
To discuss custom testing configurations or request a hardware quote, you can fill out the quote request form directly on the Instrument Transformer Testing page. For immediate engineering consultations regarding HAEFELY/Tettex systems, contact our headquarters in Manassas, VA, at (703) 365-2330 or via email at hvsales@hvtechnologies.com.