Megger TPT420 LCD/LED Two-Pole Voltage Tester

Product Information

Instrument transformers perform the important function of providing windows on the power grid’s electrical behaviour. Protection, control, and measuring devices require these ‘windows’ yet they also need electrical isolation from the grid as they function at much lower voltages and currents. Instrument transformers provide the solution; they are go-betweens that provide isolation by magnetically coupling secondary monitoring and measuring devices to the grid. There are several types of instrument transformers, but one of the most common on higher voltage transmission systems is the coupling capacitor voltage transformer (CCVT).

CCVT construction varies between manufacturers, models and year of fabrication. Knowledge of the construction is critical when deciding what and how to test. As mentioned previously, some CCVTs are equipped with a potential grounding switch located below C1, at the intermediate voltage terminal (IVT), and a carrier grounding switch below C2 at the low voltage terminal (LVT), as shown in Figure 3. In some CCVTs, however - mainly modern types - the low voltage terminal may not accessible. Understanding the construction characteristics and location of the IVT and LVT is therefore important when determining appropriate connections for testing and deciding whether the ground switches need to be open or closed for the required measurements to be made.

Megger TPT420 LCD/LED Two-Pole Voltage Tester Technical Specifications 

Power frequency (50 / 60 Hz) power factor / tan delta testing has been the standard for evaluating the condition of solid and liquid insulation in transformers for over 100 years.With the introduction of 1 Hz power factor / tan delta testing, Megger is revolutionizing insulation diagnostics. When testing at 1 Hz, the dielectric losses due to moisture, contamination and increase liquid conductivity are better observed. Power factor or tan delta test at 1 Hz provides superior detection sensitivity to early and advanced insulation deterioration. Combined with power frequency measurement, 1 Hz delivers immediate insulation assessment without the need for trending or proprietary databases. Works below the tipping thresholds of RCDs, RCBOs and safety breakers when testing circuits between phase and earth For a motor in normal operation, which has not endured significant electro-mechanical thinning of the insulation, the surge-test voltage is far below the dielectric strength of the insulation. A basic ratio test can be carried out by exciting the primary side of the CCVT with a 10 kV source and measuring the secondary voltage with a digital multimeter. However, this supplies no measurement of phase deviation, which is required to validate the accuracy of the CCVT.

For compliance with the highest safety standards the Megger TPT420 arrives with GS38 probe tip shrouds as standard, along with a protective storage and carry pouch. Key Features As mentioned in the previous article, there are many options for testing insulation, and Megger supplies an extensive range of testers for such applications, from 50 V to 15 kV insulation testers, through VLF and AC Tan Delta test sets to diagnostic Dielectric Frequency Response instruments and, under the Baker brand, specialist motor testing equipment up to 40 kV. Transformers are an integral part of the power grid. Their reliability directly impacts the reliability of the grid. The failure of this critical asset can handicap the grid and increase its volatility. Because replacing a high voltage transformer requires planning for many reasons, including long manufacturing lead times that can exceed a full year, it is widely accepted that asset management, particularly of transformers, is a beneficial contribution to the operation of the grid. The MET1000 All-in-one true RMS electrical tester is a multifunctional voltage andcurrent tester that gives electricians and electrical engineers a versatile and robust handheldmeterwith detachable test leads. Featuring both LED and LCD displays, it gives youa 200 A AC and1000 V AC/DC tester designed for everyday use. CATIV 600 V/CATIII 1000 V rated, with an IP65 housing for added protection, it reduces the number of testers required in the professional’s tool bag.These on-line techniques, of course, cannot tell you about all types of incipient faults. Indeed, when warnings are given, a full diagnosis may require complementary off-line testing. In addition, off-line tests are often used on their own in a planned maintenance regime that takes motors off-line for testing and other maintenance activities at appropriate intervals. Compared with on-line tests, off-line tests provide different insights into the motor’s condition; the two approaches to testing are, therefore, complementary. Furthermore, the Megger TPT420 LCD/LED Two-Pole Voltage Tester supports single-pole voltage tests and simplified phase rotation indication tests which avoid crossing the test probes. Moreover, when testing circuits between phase and earth, the Megger TPT420 LCD/LED Two-Pole Voltage Tester will work below the tipping threshold of RCDs, RCBOs and safety breakers to prevent unintentional disconnection. And it’s the same with a surge test generated by a Baker DX tester. It applies a voltage and rise-time to enable you to see the inter-coil response, but with a signal controlled in voltage, time and energy, so that the impact on the motor is similar to the spikes that the motor receives as a result of typical power-system variations during everyday operation.

CCVTs are devices capable of dual function. One function they can perform is to provide highly accurate voltage conversion for measuring devices, protection relays, and automatic control systems, while the other is to couple high-frequency power-line carrier (PLC) signals onto the transmission system for communication and control purposes. Ratio validation to confirm that the performance of the CCVT matches its nameplate values for ratio and phase accuracy requires the use of specialised test equipment. For this reason, it is not commonly carried out in the field. If validation testing is performed, however, the results should fall within the appropriate accuracy parallelograms given in standards, such as IEEE C57. 13- 2016. One such example is provided in Figure 2, wherein a CCVT is used for metering purposes.

Finally, this ergonomic tester is equipped with a bright LED torch, GS38 probe tip shrouds, and an IP64-rated housing. The Megger TPT420 is also supplied with a carry pouch.