TM1700 circuit breaker analysers

The TM1700 series of time and travel analysers are designed to test medium and high voltage AC circuit breakers. These instruments will test one or two breaks per phase circuit breakers and perform up to six motion measurements simultaneously. It is designed to work at all voltage levels, including 765 kV substations. The TM1700 can also test circuit breakers of four and six breaks per phase if the breaker is tested phase-by-phase.

CABA Win has a built-in wizard called the Test Plan Editor (TPE) that is used to create custom test plans. You can easily select the test types, parameters, and pass/fail values on just a couple of screens. Once you have created a test plan, it can be duplicated to test different breakers and edited in case certain parameters are changed. CABA Win features more than 500 parameters, from universal ones applicable to all breakers to unique parameters for specific breaker models. Therefore, no function will be left untested.

All TM1700 units, with an on-board computer or without, can be controlled with your PC as long as it has CABA Win installed.

The TM1700 instruments do not supply power to the circuit breaker. It has a close and open switch that will activate an internal contact to apply external power to the circuit  breaker. Station power is typically used, and will be measured by the control module. In the case of commissioning or minimum voltage type tests, Megger has a B10E accessory, a power supply designed specifically for circuit breakers.

Megger has two other analysers: the EGIL and the TM1800. The EGIL is designed for simple on-screen operation, providing your standard time and travel analysis in a small package. The TM1700 allows you to fully customise your test plans and provide a wide variety of advanced testing. The TM1800 is a modular system that allows you to expand your testing as your needs develop. It is very well suited for older air blast circuit breakers where up to 10 or 12 breaks per phase may be required. 

SDRM stands for Static and Dynamic Resistance Measurement. Static Resistance Measurement (SRM) is a basic ‘DLRO’ or ‘DuctorTM’ test, where a test current is injected through the circuit breaker, and a voltage drop is measured to calculate the resistance value of the contacts. Circuit breaker SRM test results are typically in the low hundreds of micro-ohms to below ten micro-ohms, depending on the breaker type. A Dynamic Resistance Measurement (DRM) is the same measurement performed while the circuit breaker contacts are moving. This test is performed on SF6 circuit breakers to measure and evaluate the arcing contacts of the circuit breaker so you can replace them as they wear out.

DRM tests are only used on SF6 style circuit breakers due to their arcing/main contact design. The test serves as a way to check that an SF6 circuit breaker’s arcing contact is significantly long enough to protect the breaker’s main contacts. Since VCBs use the same contact for arcing and current transmission, the DRM test is not applicable.

You can test breakers in many ways, but one of the most common tests is timing of the main contacts, which directly indicates the trip time. A typical procedure on a circuit breaker that is in service is:

1. Open the breaker 
2. Disconnect the breaker by opening the disconnect switches
3. Ground the breaker
4. Perform timing test

Will the timing tests show the true trip time? Not necessarily! Consider a breaker that has been in service without operating for months, or years, before it was taken out of service for testing. It could then suffer from a lack of grease, or dried grease, and corrosion in its bearings. These problems can and probably will slow down the first operation.The problem with the procedure above is that the circuit breaker has been operated at least once before testing begins. This operation might be all it takes to eliminate corrosion problems or sticky bearings and bring the breaker’s trip time up to standard. So when the actual timing test is performed, no problem exists. The service engineer thinks the breaker is in good shape and no further service is needed. Some months later, the corrosion is back, and when a fault occurs, the breaker does not trip fast enough, or maybe not at all. Therefore, capturing the first operation to reveal any problems with the circuit breaker is essential.

DualGround™ is a test method developed by Megger to perform timing while the circuit breaker is grounded on both sides. This allows you to always work between safety grounds, thus negating induced current that flows through the test equipment under normal timing conditions with only one side grounded. Megger uses a patented Dynamic Capacitance Measurement (DCM) that has a simple hookup and accurately measures the contact times of the arcing contact, per IEEE and IEC. With DualGround™ timing, you can test the circuit breaker safer and faster than with traditional timing methods.

The TM1700 instruments will test both pre-insertion and post-insertion resistors. They will measure and calculate several parameters for the PIR, including PIR contact time and insertion time. The TM1700 can also measure the value of the PIR as long as it is within the range of 10 Ω and 10 kΩ. 

Multiple configurations of the TM1700 are available, so it depends on the type of testing you want to perform. All configurations will operate the circuit breaker (using station power), time up to two breaks per phase, and record digital motion (up to six channels simultaneously). If linear transducers are needed for testing, then the unit will need the analogue option. You will need extra analogue channels if more advanced testing is required (DRM, First Trip, Vibration). The smart control module will measure one ‘A’ and one ‘B’ contact through the control circuitry. If you need to measure extra Aux contacts or coil currents for circuit breakers with more than one mechanism (IPO), you will need two control modules and the Aux module (TM1720, TM1750, TM1760). The TM1700 comes in standalone operation with an on-board computer or computer-controlled options.

Once a TM1700 instrument is built, the hardware is fixed. You can add several accessories later as long as the unit has enough inputs to use them (DCM, SDRM, First Trip). If you’re unsure of what is to be tested, or want to leave the option of expanding your testing portfolio till later, then choosing the TM1760 with an extra analogue channel will offer you the most flexibility.

At first, measuring travel on circuit breakers can be intimidating because many connection options exist, and a few settings are required. Therefore, some may choose only to measure timing. By only measuring timing, however, the test may only detect problems after damage has been done to the circuit breaker. You will assess the mechanism’s full stroke and the contacts by measuring travel along with timing. Any overtravel or excessive rebound can be measured and corrected before the circuit breaker contacts reach mechanical failure.

With the multitude of circuit breaker manufacturers and designs in the field, there is no one size fits all transducer. When considering what transducer to use, the best option is to consult the manual or contact the manufacturer to see what transducer they recommend and if any special hardware is needed to connect. If there are a variety of circuit breakers in your fleet, three main kits will cover what is required by most of them. Megger has a 600 mm bulk oil circuit breaker (OCB) kit, a 300 mm SF6 dead tank kit, and a rotary mounting kit. Note: there are still some breakers that may need specific mounts or transducers. Consult the circuit breaker accessories guide for a list of transducers and kits available.

Since the life of a circuit breaker is measured in decades and not years, Megger knows that consistency and compatibility are of the utmost importance when it comes to circuit breaker testing. Old test plans are compatible with the latest version of CABA Win and the TM1700. The software will automatically allocate the channels for proper testing the first time loading the test plan. If new features want to be added or changed, you can use the Test Plan Editor (TPE) for modifications. 

CABA Win includes breaker-specific test plans for multiple CB manufacturers and types, pre-programmed with the correct speed calculation points and pass/fail values. Additionally, the easy-to-use Test Plan Editor (TPE) application can modify existing test plans if your breaker specifications or testing parameters vary.