Megger TPT420 LCD/LED Two-Pole Voltage Tester

Product Information

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. The Megger TPT420 voltage tester is designed to provideelectricians and electrical engineers with an easy-to-use voltage indicating instrument. The meter will continue to warn the operator of dangerous test voltages even when the batteries are exhausted. With both LCD and LED displays, the TPT420provides both AC and DC voltage measurement from 12 to 1000 V AC and up to 1500 V DC. In addition, a continuity function within the range 0 to 500 kΩ, is included and for added safety, continuity, and voltage measurements are also accompanied by an acoustic sounder. 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.

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.

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

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. The EMU, in addition to an inductive voltage transformer, contains a tuning circuit and protection against ferroresonance (Figure 1). The tuning circuit is a reactor that compensates for magnitude errors and phase shift caused by the CVD, making it possible to have the CCVT with a characteristic on the secondary side that is similar, in terms of error and phase deviation, to that of a purely inductive voltage transformer. A bad turn will short and this will be shown by a jump in the ringing frequency of the coil (it becomes in effect a ‘different’ coil at this point in the test). Large frequency jumps can be clearly seen on the tester display, but the instrument’s software also uses mathematical analysis to reveal anomalies that are less easy to spot by eye. 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.

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. In some circumstances, the CVD capacitive reactance can resonate with the magnetizing reactance of the inductive voltage transformer and the compensating reactor cores. This unwanted effect is called ferro-resonance and can give rise to large and damaging voltages across the inductive and capacitive elements. To avoid this, a ferroresonance damping circuit is installed in parallel with one of the secondary windings. 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: 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.

What’s Included?

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. 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. 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. 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.