Purpose and Standards of Measuring Transformer Voltage Ratio & Vector Group
Transformers are an essential component of electrical systems that allow for the efficient transmission and distribution of electrical power. Ensuring that transformers are operating correctly is crucial, and one way to accomplish this is by measuring the transformer voltage ratio and vector group.
The voltage ratio is considered to be the ratio between the no-load voltages of HV- and LV-side. Vector groups and their characteristics are only defined for poly-phase transformers. They can be connected instar-, delta- or zigzag-connection, depending on the requirement. The phase displacement between the windings can only be influenced within 30° - steps from 0° to 330°, which depends on the connection method. Transformers' parallel operation needs a similar no-load ratio and the same vector group. Otherwise, circulating currents would occur between the parallel transformers, which have to be avoided. The voltage ratio and the phase displacement are principally of interest when it comes up to parallel operation with two or more transformers.
Standard of measurement transformer voltage ratio & vector group
IEC60076-1Clause 6: "Connection and voltage displacement symbols for three-phase transformers" Clause 10.3: "Measurement of voltage ratio and check of phase displacement"
IEEEC57.12.90Clause 6: "Polarity and phase relation test" Clause 7: "Ratio tests"
The most common vector groups according to IEC 60076-1
Measuring transformer voltage ratio and vector crew is indispensable for preserving suited functioning, detecting faults, facilitating maintenance, and making sure appropriate installation. Additionally, these measures can stop extreme harm to tools and enhance strength efficiency. Therefore, it is imperative to behavior these checks commonly and accurately, with precision devices and by means of educated professionals.