Measuring Test Instruments Practical
Background and Introduction
The main objective for this experiment is making sure the electrical equipment is safe to use. To avoid from electric shock.The experiment is divided into two parts——Insulation Resistance Test and Earth Continuity Test. Measuring the values by using Multmeter, Insulation Tester and Power Factor Meter.
Single Phase Socket Outlet is the type which is found most often in houses. The other type, three-phase, is usually only found in industrial or possibly commercial locations.
A single phase power socket is the type of socket that people are most familiar with. Although designs of these vary from country to country, they consist of three sockets for a plug: a live conductor (where current comes from) a neutral conductor (where current goes to) a bonding conductor (bonds chassis for some devices to system's low potential, i.e. ground)
A single-phase power socket differs from a poly-phase (e.g. a three phase) socket because a single phase system consist of only 1 phase (hence the name). A Three phase socket would need conductors for phases A, B, and C, and perhaps a neutral conductor depending if the three phase system is configured in delta or wye.
It should also be noted that, especially in North America, that 240V, outlets are also single-phase. These outlets are also only single phase.(From Ref No.1)
Industrial (Three Phase) and multiphase plugs and sockets provide a connection to the electrical mains rated at higher voltages and currents than household plugs and sockets. They are generally used in polyphase systems, with high currents, or when protection from environmental hazards is required. Industrial outlets may have weatherproof covers, waterproofing sleeves, or may be interlocked with a switch to prevent accidental disconnection of an energized plug. Some types of connectors are approved for hazardous areas such as coalmines or petrochemical plants, where flammable gas may be present.
Almost all three-phase power plugs have an earth (ground) connection, but may not have a neutral because three-phase loads such as motors do not need the neutral. Such plugs have only four prongs (earth, and the three phases). An example of a socket with neutral is the L21-30 (30 A) and the L21-20 (20 A) both of which have five pins (earth, neutral, and X, Y, Z phases).
While some forms of power plugs and sockets are set by international standards, countries may have their own different standards and regulations. For example, the colour-coding of wires may not be the same as for small mains plugs.(From Ref No.2)
Insulation Resistance Test, for this test values are not direct shown us. The resistance value is come from Ohm’s Law——Use the values of known voltage divide the values of the current which we measured.
Earth Continuity Test, is for checking the connection inside the socket. The qualified socket is suppose to have 0.1 ohms resistance which means no resistance though connection.
This is the equipment we used during the experiment.
A multimeter or a multitester, also known as a VOM (Volt-Ohm meter or Volt-Ohm-milliammeter ), is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter would include basic features such as the ability to measure voltage, current, and resistance. Analog multimeters use a microammeter whose pointer moves over a scale calibrated for all the different measurements that can be made. Digital multimeters (DMM, DVOM) display the measured value in numerals, and may also display a bar of a length proportional to the quantity being measured. Digital multimeters are now far more common but analog multimeters are still preferable in some cases, for example when monitoring a rapidly varying value.
A multimeter can be a hand-held device useful for basic fault finding and field service work, or a bench instrument which can