Specification of voltage regulating distribution transformers (VRDT)
IEC 60076-24-2020 pdf download.Power transformer -Part 24: Specification of voltage regulating distribution transformers (VRDT)
Transformateurs de puissance — Partie 24: SpecificatIon des transformateurs distribution rgulateurs di
tension (VRDT).
11.1 Routine tests
Apply IEC 60076-1 and IEC 60076-11, but with different test sequences, in accordance with this document.
11.2 Functional tests
With the regulating unit fully assembled on the transformer, the following sequence of operations shall be performed as a routine test, without any failure:
a) with the transformer dc-energized, three complete cycles of operation (a cycle of operation goes from one end of the tapping range to the other, and back again);
b) with the transformer de-energized, and with the auxiliary voltage reduced to 85 % of its rated value, one complete cycle of operation;
c) with the transformer energized at rated voltage and frequency at no load, one complete cycle of operation.
11.3 Type tests
If the regulating unit contains electronic components, the test conditions shall be agreed
between manufacturer and purchaser.
If the operation of the regulating unit occurs in conditions that differ from those of IEC 60076-i. a heat run test according to IEC 60076-2 shall be agreed between purchaser and manufacturer.
With the regulating unit fully assembled on the transformer, the following sequence of operations shall be performed, without any failure:
With one winding short-circuited and, as far as practicable, rated current in the tapped winding, 10 cycles of tap-change operations across the complete range.
NOTE In order to check the correct coordination of over-current protection and to have all information regarding the operation of the VROT. the purchaser can request the measurement of the Impedance voltage and load losses on all the taps, related to the high voltage (HV) rated voltage and rated power of the VRDT.
The functional tests shall be repeated.
11.4 Special tests
The transformer, including the regulating unit, shall pass the short-circuit withstand test in accordance with IEC 60076-5.
If the regulating unit contains electronic components, the test conditions shall be agreed between manufacturer and purchaser.
11.5 Tests for the control unit (electronic or data transfer part)
11.5.1 Functionality test during erection and commissioning
The transformer is connected on either the HV or LV side and the other side is open for testing.
Voltage shall be measured at the open side.
The control unit Is in manual operation mode and is then switched through the complete regulation range.
For each switching operation, the relative change in the measured voltage shall be equivalent to the regulation steps.
If the VRDT has an automatic mode then with rated voltage applied to the HV, manually set the regulator to one of the extreme positions. then switch to automatic mode and check that the system regulates the LV voltage to the rated value.
11.5.2 Type tests
The VRDT shall satisfy the following criteria:
• safety requirements according to IEC 61010-1 and IEC 61010-2-201;
• electromagnetic compatibility according to IEC 61000-6-2, IEC 61000-6-4 and IEC 6 1000-6-5 with performance criterion A. Any higher performance levels shall be agreed between purchaser and manufacturer;
• degree of protection of lP3O according to IEC 60529. Any higher degree of protection shall be agreed between purchaser and manufacturer;
• environmental conditions according to IEC 60068-2-1 (up to —25 °C for 96 h), IEC 60068-2-2 (up to 70 °C for 96 h). IEC 60068-2-30 (up to 55 C for 24 h in 6 cycles) and IEC 60068-2-78 (up to 40 C for 96 h at 93 % humidity). If the environmental conditions may lead to a higher risk of corrosion, tests according to IEC 60068-2-11 shall be agreed between purchaser and manufacturer;
• if a test of vibration and shock is required by the purchaser in the specification, unless otherwise specified this shall be In accordance with IEC 60255-21-1 and IEC 60255-21-2.
Generally, any higher requirements shall be agreed between purchaser and manufacturer.IEC 60076-24-2020 pdf download.