INSTRUMENT TRANSFORMER TESTING
Portable instruments for testing CTs, PTs and CVTs
In high revenue areas such as universities, shopping malls
and business centres, taking CT's offline for testing is not
an option, so a reliable live CT test alternative is required.
Live CT testing using admittance...
A component of a good CT's characteristic performance is
a low admittance value. This admittance value can be measured while in-circuit using the 505B (pictured).
The 505B is placed in series with an in-circuit CT and it
superimposes a small 1.6kHz signal onto the live 50 or 60Hz
secondary metering circuit.
A filter on board the 505B extracts the 1.6kHz admittance
reading and from this a quick determination is made on the
CT's general health.
Admittance testing only adds an extra 10 minutes to a polyphase
meter test and is quickly becoming part of a routine test requirement
for some utilities.
The 505B can perform the following measurements:
Voltage and current at 50 or 60Hz.
1.6kHz admittance test on a CT secondary.
1.6kHz admittance test on a CT secondary plus the complete metering loop.
VA burden of the metering loop downstream from the test block, or at the CT secondary terminals.
VA burden of the metering loop from VT secondary terminals or at its test block.
A USB interface is also provided on the front panel for downloading results data to a PC.
Performing field test measurements of Current and Potential
Transformers has been made far simpler with the Model 590J.
This full featured product combines all of the metering CT test
abilities of the popular 590G-V2 model with the additional advantage
of also being able to perform both protection CT excitation tests as
well as Full Load inductive PT tests.
The 590J eliminates the need for additional bulky accessories usually
required to perform various tests on different types of equipment,
saving the operator valuable time and money.
Light weight and portable, the 590J is housed in a ruggedized
plastic case and is supplied with the necessary test cables and
attachment accessories. It is further packaged in a foam lined
transit case for safe transport.
It features the following offline test capabilities:
- CT ratio and phase error measurements to an accuracy
- Excitation measurements on protection Class CTs.
- Simulated Full Load inductive PT testing on up to 2 windings.
- No Load inductive PT testing.
- CT 1.6 kHz Admittance test.
- CT and PT Burden test.
- CT and PT winding resistance.
- CT and PT polarity check.
- Batch testing of metering CTs.
- Automatic Class assessment.
- Record download to USB Flash or PC
This full featured CT and PT test instrument lowers testing costs by being simple, fool-proof and fast.
It's capabilities allow utility personnel and test technicians to pursue the very important task of testing field based instrument
transformers for the detection of equipment tampering, measurement losses and faults.
Since 1999, Red Phase Instruments has led the way in the manufacture of portable CT error testing equipment.
Our portable analysis method has allowed utilities around the world to test their metering CTs easier and faster than using bulky traditional methods without jeopardizing accuracy.
Following feedback from our users, our Model 590G-V2 is the latest version of this successful and well proven CT error tester.
The 590G-V2 has all the features and advantages of the previous models with additional testing features, better accuracy and smaller size and weight.
In a world where cost control is gaining importance, this CT tester not only lowers testing costs by being simple, fool-proof and fast. It also allows utilities to pursue the very important (yet at many times forgotten) task of testing installed CTs for detecting tampering, and minimizing losses due to faulty CTs.
CT Ratio and phase error measurements to an accuracy of 0.02%.
CT 1.6 kHz Admittance test.
Graphical display or plot of the CT's excitation curve.
Measures CT winding resistance.
Performs a CT polarity check.
PT full load simulated tests (with 590D-1 accessory)
Live CT testing (with 590F accessory)
For customers who cannot be disconnected or offline when performing
metering CT tests, the 590F1 HV (High Voltage) accessory can be added
as a retrofit kit to our popular 590C, 590G and 590GV2 CT testers.
The first part of the kit is the clamp on CT unit which is mounted on
the end of a hot stick. This unit has a battery powered electronic
compensation circuit for the clamp on CT ("clipon") which greatly
improves accuracy over a wide operating range, typically 25A to 1450A.
A microprocessor is also used to control the clipon compensation,
manage the internal range changing and provide communications via
a fibre optic and RS-485 interface.
The fibre optic cable runs between the 590F1 and a small interface unit at the base of the hotstick.
From there the signal is transmitted through a 100M drum of RS485 cable to the 590C/G or G-V2
The combination of hot stick and cable has been tested to 100kV, line to ground.
The actual breakdown voltage of the hotstick and fibre optic cable is much greater than 100kV,
but for operator safety we suggest not using this test set above 100kV. However, with a longer
hotstick and suitable precautions the 590F1 unit can be used at higher voltages.
The CT primary current measured by the clipon is sent via the cable to the 590C/G or G-V2 CT Tester which can be up to 100M away. Extra drums can be daisy chained up to 400M in total. The 590C/G or
G-V2 unit measures the CT secondary current, 5A, 1A or lower, and then calculates the CT ratio and
phase error to an accuracy of 0.1%.
For testing live LV Low Voltage or low current CTs, we have a variety of electronically compensated
clamp on CT's, "Clipons". Let us know what you require and we can adapt the 590F to suit.
We have two regular low to medium voltage clipons. One is for cables carrying up to 1,000A and the other is a large jaw clipon for busbars up to 2,500A.
This is an accessory to the model 590G-V2 and is used to
perform full load testing of inductive PTs. It has a high power switch mode ( typically 1.2kW ) source for full load performance testing of PTs under simulated load conditions to 0.1% accuracy. It uses the existing measuring and processing functions of the 590G-V2 in combination with its own processor controlled monitoring and interface systems.
Communication between the two units is via a serial link.
The 590D-1 unit is the interface between the 590 model series and the inductive PT under test.
The 590D-1 measures:-
Primary & Secondary winding resistance.
Secondary winding admittance with primary short circuited.
Primary winding admittance calculated from turns ratio.
Turns ratio and no load voltage ratio.
Secondary admittance with primary open circuit.
Finally the microprocessor calculates the PT errors at 6 test points from the measurements taken.
These test points are typically taken at 25% and 100% of the burden rating over 80%, 100% and 120%
of rated voltage.
The 590D-1 comes with these default or standard test points already preset / programmed but the
operator is also able too add their own set of custom test points to suit via the 590C/G or G-V2 model.
True burden based CVT analysis done portably!!
Ability to test for ratio errors at up to 500VA burden.
Selectable Power Factor.
Ratio error accuracy to 0.05%.
Four selectable CVT test point standards to choose from.
Tests CVT rated to 500kV with up to 3 secondary windings.
Truly portable ~ 20kg.
This is not a simple ratio / nameplate comparison tester.
The R & D that has gone into developing this instrument is second to none.
Over 60 CVT's from over 12 manufacturers have been carefully characterized under lab and field conditions to create a complex software
model that is able to measure a known CVT down to a 0.05% ratio error and even an unknown CVT to only
a 0.25% error under real load conditions.
Under test conditions the 590K takes a number of measurements and characterizes the CVT.
It then calculates the performance of the CVT under different loads and applied voltage conditions to suit any of the four common test types used on a CVT. If other test points are required, Red Phase Instruments
is able to modify these points to suit any regulation.
So when compared to traditional methods the 590K stands out as the only real portable alternative for real load ratio assessment over a wide VA range and flexible Power Factor settings.
The CVT tester uses a combination of a Digital Signal Processor and a PC104 mini computer to provide a powerful and yet easy use instrument running on a Windows XP operating system. A large colour display on the front panel presents a large amount of easy to follow information.
This small battery powered tester is ideal for carrying out
quick burden checks in CT metering and protection circuits.
The clipon CT (pictured) is connected to the CT secondary wiring and the crocodile clips attached to the CT terminals.
The instrument calculates the burden as the ratio of voltage over current.
The burden measurement accuracy is typically 1% at 5A and 5V, and decreases to 5% at 0.01A and 0.01V.
REFERENCE CT: MODEL 590-RT
Our 590 reference CT is a valuable multi-tap reference platform for the calibration and accuracy of our 590 series of CT Testers.
Multiple primary turns are fitted to increase accuracy for testing low ratio CTs. The error of a reference CT is very dependent on the ratio selected for testing. These are not electronically compensated, and have errors that are better than 0.01% for higher ratios.
The reference CT comes in a rugged pelican case with a selectable tap switch and terminal posts for connection..