Megger TPT420 LCD/LED Two-Pole Voltage Tester

Product Information

Validation of insulation, ratio and burden at rated voltage requires large and heavy test equipment used in conjunction with expensive instrumentation. For this reason, these tests are commonly used during the manufacture of CCVTs but are impractical in the field. Nevertheless, field measurements of the CCVT burden, as an aid to ensuring that the burden rating of the device is not exceeded, are possible. 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. 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.

In addition to this, the Megger TPT420 LCD/LED Two-Pole Voltage Tester features a Continuity function which will alert the user to the presence of continuity between 0 and 500kΩ via a visual and audible alert. The Megger TPT420 LCD/LED Two-Pole Voltage Tester will also issue an audible alert upon detection of voltage and will continue to warn the user of dangerous test voltages even when its batteries have expired. This voltage tester has a safety rating of CAT IV 1000V. When testing motors, it’s important to keep in mind that they are complex electro-mechanical devices with a complex set of failure modes and related diagnostic options. We will look at the failures of motor electrical/insulation systems, how to manage the life of motors by adopting an appropriate test regime and the concerns that are sometimes voiced about the ‘high’ voltages used for surge testing. 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.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).

To answer these questions, let’s look at an example. When a 415 V motor is assembled, the insulation applied to the wire used to wind the stator has a dielectric strength of approximately 8000 V. During its lifetime, this insulation will degrade primarily due to heat in the motor, but also as a result of environmental conditions and the coil movements which arise from starting, stopping and load changes. The Megger TPT420 Two-Pole Voltage Tester is designed to provide electricians & electrical engineers with a simple, intuitive voltage indicator compatible with both AC and DC voltages. This device can measure AC voltage between 12 to 1000 V and DC voltage between 12 to 1500 V. The TPT420 will even continue to alert the user of a present voltage once the batteries have been completely exhausted. Including a continuity function within 0 to 500 kΩ and a frequency range of 40 to 400Hz, this unit can be applied to numerous situations such as automotive, fire alarm & solar/PV systems.

Megger VF5 Voltage Tester Technical Specifications 

In fact, it will typically take the pulse 100 ns to travel from one coil-turn to the next, which is equal to the rise time of the pulse. The result is that the pulse produces a significant voltage difference between adjacent turns of the coil, something that it is impossible to achieve with any other test technique. The surge test will, therefore, reveal turn-to-turn insulation weaknesses. 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. 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. 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. The Megger TPT420 LCD/LED Two-Pole Voltage Tester is an AC/DC voltage indicator. It can detect and measure voltages between 12 and 1000V AC and 12 and 1500V DC. The detected voltage range is indicated on the LED scale while the numerical reading is displayed on the LCD.

Capacitance and line frequency power factor (PF) measurements should be made routinely on CCVTs. Insulation power factor tests are most informative when the amount of insulation included in the test is minimised. For this reason, tests are performed on each individual component of the CVD (e.g., C1-1, C1-2, …, and C2). Typical overall PF values range from 0.2 % to 0.5 %, but power factor values under 0.05 % are normal depending on the insulating materials used for construction. Go/no-go tests are an invaluable part of every maintenance regimen. Options include insulation resistance, leakage current, polarisation index and step voltage testing, and there are few who would argue against the benefits of these core electrical tests. However, these tests will not reveal one of the most common early initiators omotor faults: inter-turn insulation breakdown. To detect such a breakdown, it is necessary to use a surge test. Unfortunately, this is the area where some confusion has been generated in relation to the ‘high’ voltages involved. In addition to the unit's adaptable auto-ranging voltage and continuity tests, the Megger MET1000 has a built-in current clamp for AC current measurement to 200 A. With true RMS AC measurements, a phase rotation test, and single pole voltage test built in, the MET1000 is a truly multi-purposeelectrical test instrument, ideal for use in commercial, industrial, and domestic environments. It even comes with GS38 shrouds, provided as standard, to ensure compliance with the latest standards.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. Figure 1 provides examples of surge traces for a good winding and a winding that has weak insulation or a turn-to-turn short. The three traces – corresponding to the three phases of the motor’s windings – should overlay as one on the graph but, as can be seen, the trace for a winding with a turn-to-turn short is different from the traces for the other two phases. On-Line testing – that is, testing while the motor is running – can also be carried out on an as-needed basis with a portable on-line monitor like the Baker EXP4000.

On older style CCVTs, the potential terminal is typically accessible. However, for modern CCVTs such as those supplied by Trench, the potential terminal is inaccessible. Even in these cases, however, C2 can still be tested. CCVTs have a potential ground switch that provides the means to ground the potential terminal. With the potential ground switch closed, the carrier terminal can be energised, a low voltage lead connected to the line terminal (top of C1), and a C2 test performed in the GST-guard mode. Note that the carrier terminal must be disconnected and isolated from ground potential and the drain coil (also, if applicable, from any accessory leads) for the C2 test. In addition, the test voltage (typically 500 V) used to energise the carrier terminal must not exceed the voltage rating of the terminal. In summary: The basic insulation tests just described can be usefully augmented by adding PF measurements at different frequencies and a tip-up test. A PF test at 1 Hz specifically, provides a better indicator of developing issues, facilitating early detection. 1 Hz PF is particularly sensitive to moisture contamination, a commonplace CCVT failure mode. Narrowband DFR tests include power factor tests at several discrete frequencies, including 1 Hz up to 505 Hz. At its core, a voltage tester is a simple device designed to indicate the presence of electrical voltage in a system or a component. The underlying principle lies in Ohm's Law. This states that the current passing through a conductor between two points is directly proportional to the voltage across the two points. When testing between phase and earth on any circuit protected by an RCD, RCBO, and Safety Breaker, the TPT420 is designed to work below the tripping threshold of these devices to help avoid unintentional disconnection. The phase rotation indication test has been simplified, which now avoids the crossing of the test probes. The TPT420 can also perform a single-pole voltage indication test.

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

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 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.