9.
12/3 Type WV
TRANSFORMER
TEST SYSTEM
n Induced AC voltage test
n Measurement of no-load loss and current
n Measurement of short-circuit impedance and load loss
n Temperature-rise test
n Special tests
TRANSFORMER TEST SYSTEM
Power supply
1 Static frequency converter
HV circuit
44 2 Step-up transformer
3 Filter/ voltage divider
4 Capacitive compensation unit
5 Voltage /current dividers
Test
Object Control system
11 2 3 5 13
6 Control Simatic S7
7 Industrial computer
8 Remote access module
9 LAN, Internet
Measuring systems
12345 12345 12345
10 Peak voltmeter
U P PD 11 Power analyzer
6 7 10 11 12
12 PD measuring system
9
13 Transformer
8
Power connections
Communication / measurement
Fig. 1 Transformer test system for induced voltage tests, based on static frequency converter, type WV 2000-4000/170 Fig. 2 Block diagram of on-site transformer test system
facts IN BRIEF Application System AND Components
The transformer test system is able to perform induced AC 1) Induced AC voltage test by exciting the low-voltage winding 3) Measurement of short-circuit impedance and load loss The central feeding source is the static frequency converter (1)
voltage tests, measurements of no-load losses and no-load of the transformer under test for the HVAC test voltage on its HV at rated current and power frequency (50/60 Hz) in three-phase [see fig. 2 ]. It supplies the active as well as the reactive power
currents, measurements of short-circuit impedances and load side. The frequency converter supplies the excitation three-phase and single-phase mode using a loss-measuring system. with variable amplitude and frequency to the test circuit. The
losses, temperature-rise tests and special tests according to the or single-phase voltage of ≥ 100 Hz, which can be adapted to A capacitive compensation unit is required. output voltage of the converter is adjusted to the required test
international standard IEC 60076 parts 1 to 3. The test system is different transformer LV windings by a finely graduated step-up voltage level by the finely graduated step-up transformer (2). The
based on a state-of-the-art static frequency converter and car- transformer with numerous taps. The standard output voltages 4) Temperature-rise test with increased feeding power to heat EMC interferences are smoothened by the filter (3). The associ-
ries out tests implementing the precise waveform with a total of the step-up transformer range from 1.5 kV to 170 kV. up the test object with the sum of load and no-load losses at ated filter capacitor is built as a divider and gives an input signal
harmonic distortion (THD ) < 5 % and a partial discharge (PD) 50/60 Hz. A capacitive compensation unit is required. to the peak voltmeter (10) for the test voltage measurement and
noise level < 10 pC. The test system is maintenance-free. And 2) Measurement of no-load loss and current at rated voltage control. An adapted and finely graduated HV capacitive compen-
with its low investment costs and minimal installation requirements and power frequency (50/60 Hz) in three-phase and single-phase 5) Special tests such as for example the determination of sound sation unit (4) enables compensation of the reactive power dur-
it has particularly low lifecycle costs. The test system is highly ef- mode. For the loss measurement the appropriate equipment is levels under no-load and load conditions or the measurement of ing the measurement of load losses or the temperature-rise test.
ficient due to fully-automatic testing procedures. Furthermore, the connected to the LV side of the transformer under test. the zero-sequence impedance(s) at 50/60 Hz. A measuring system consisting of voltage and current measuring
modular design of the test system allows for future expansions. units (5) and a power analyzer (11) are applied for precision pow-
er measurements. The computer control (7) together with the
control Simatic S7 (6) enables automatic execution of complex
test procedures as well as data storage in a central database for
further evaluation or even generation of a complete transformer
test protocol (HIGHVOLT-Suite®). The test system is rounded off
by a multi-channel PD measurement system (12).
BENEFITS
n THD < 5 % n modular design ALLOWS FOR n Low noise emission
n PD NOISE LEVEL < 10 pC FUTURE EXPANSIONs n maintenance-free
n freeLY adjustable frequency n ACCURATE LOSS MEASUREMENT n LOW INVESTMENT AND LIFE-
40 TO 200 Hz DUE TO QUARTZ oscillator CYCLE COSTS
stable test frequency
TRANSFORMER TEST SYSTEM
TECHNICAL PARAMETERS
1 Power ratings
One of the most important parameters of a transformer test sys- of active and reactive power of the test system. For standard test
tem is the available active and reactive power for exciting the systems and corresponing test parameters refer to table 1.
transformer under test. The required test power depends on the
power and voltage rating of the transformers under test and the 2 Sine wave shape
specific design as well as on the tests to be performed. During The test system completely fulfills the requirements of IEC 60076
the induced AC voltage test the transformer under test is a linear, defining a THD < 5 % of the test voltage. Fig. 4 shows a typical
mostly ohmic-capacitive load. The required test power is low but oscillogram of the output voltages of the transformer test system
increases with increasing test frequency. while testing a power transformer at 150 MVA. Despite an ex-
In case of the measurement of no-load loss at 50/60 Hz, the treme non-linear current consumption (THD of transformer cur-
transformer under test is fully excited and the no-load current rent 52 %), the achieved THD of the test output voltage does not
contains a considerable amount of harmonics. The transformer exceed 3.5 %.
under test represents a non-linear load. The required test power
is low but the test power source should behave like a very stiff 3 PD level
AC power supply to avoid interferences from the noload current The maximum PD noise level measured according to IEC 60270
harmonics on the test voltage wave shape. In contrast, the trans- does not exceed a level of 20 pC. The test system therefore
former under test represents a linear and ohmic-inductive load completely fulfills the requirements of IEC 60076-3.
during the measurement of short-circuit impedances and load
loss and the temperature-rise test. The temperature-rise test re- 4 Frequency
quires the highest values of active and reactive power to be fed One of the major advantages using a static frequency converter
to the test object. The static frequency converter delivers the as heart of the transformer test system is the continuously vari-
active and a minor part of the required reactive power. The main able frequency from 40 to 200 Hz. As a result, only one static
part of the reactive power has to be provided by an adapted frequency converter is used as central power source for all the
and fine graduated capacitor bank (HVC). Fig. 3 illustrates the loss measurements at 50/60 Hz as well as for the induced volt-
reactive-active characteristic of a 2 MW/4 MVA test system at age test with usual test frequencies ≥ 100 Hz. The test system
50 Hz, as well as with a HV capacitor bank of approximately 100 has a quartz-oscillator-stable output frequency (±0,01 Hz) which
Mvar. Each point under the curves is one available combination is the basis for precise measuring results.
P [ MW] 3 phase 1 phase 3 phase with HVC Test Voltage [kV] Test Current [A]
2
9,0 24
(U) (V) (W)
(U) (V) (W)
6,0 16
3,0 8
1
0 0
-3,0 -8
-6,0 -16
-9,0 -24
-4 -2 0 2 4 96 98 100 Q [Mvar] 0 10 20 0 10 20
Time [ms] Time [ ms]
-Q diagram of test system
Fig. 3 P Fig. 4 Test voltage and current waveform – no-load loss measurement
(three-phase and single-phase at 50 Hz) with THDu < 3.5 % and THDi = 52 % (150 MVA transformer)
Table 1 Standard test systems and corresponding parameters
Test system WV 620/1200 WV 1000/2000 WV 1500/3000 WV 2000/4000 2x WV 2000/4000
Active power 620 kW 1000 kW 1500 kW 2000 kW 4000 kW
Apparent power (converter) 1200 kVA 2000 kVA 3000 kVA 4000 kVA 8000 kVA
Reactive power (compensation) 12 Mvar 24 Mvar 48 Mvar 100 Mvar 200 Mvar
Max. output voltage 80 kV 80 kV 80 kV 170 kV 170 kV
Transformer to be tested 50-100 MVA 100-220 MVA 220-400 MVA 400-630 MVA 630-1000 MVA
For further information please contact: HIGHVOLT Prüftechnik Dresden GmbH Phone +49 351 8425-700
Marie-Curie-Straße 10 Fax +49 351 8425-679
01139 Dresden E-mail sales@highvolt.de
Germany Web www.highvolt.de
© HIGHVOLT Prüftechnik Dresden GmbH – 2014/09-9.12/3 – Subject to change without prior notice
