Technical library

p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 10.0px Times} span.s1 {font: 10.0px Helvetica} Since there is no such thing as perfect insulation, if any conductor is raised to a potential above that of earth some current is bound to flow to earth from that conductor. The amount of current that flows is dependent on:Voltage on the conductorThe capacitive reactance between the conductor and earthResistance between conductor and earthCurrents that flow to earth are called leakage currents and are usually very small values, typically < 1 mA. However the amount of current that is required to cause distress or harm to a human being or animal is also small, these currents must be limited by circuit design to safe values.If this is not possible, then a 30 mA RCD (residual current device) or 30 mA RCBO (residual current device with overload protection) should be fitted for personal protection.

A Portable Appliance Tester (PAT) is an instrument that is dedicated solely to the safety testing of portable electrical equipment in accordance with recognized national and local standards. Depending on locale, these standards may have been enacted into law. They may be requirements of specific industries or trade organizations, or just a good idea. In many cases, manufacturers of electrical consumer products who wish to export to foreign markets will be required, sometimes by national law, to assure the products have been safety tested. If testing is performed at time of manufacture, it will save money, aggravation and ill will that could result from having the products fail in the destination country. 

A comprehensive guide to testing power quality.

p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Times; color: #e12000} p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 12.0px Times; color: #797979} span.s1 {font: 12.0px Times; color: #797979} No electrical test is simpler...and few more commonly employed…than the continuity test. This simple test is a ubiquitous option on multimeters (DMMs) and insulation testers. It is simple to perform; connect two leads across opposite ends of the test item (IUT), press the test button, and within seconds you have the resistance reading. Low is good, high is bad. It’s so simple and easy that it is readily applied to testing situations that require a more rigorous performance from the test instrument. This article will examine the parameters that determine the separation between the types of instrumentation.

While the share of installed cables without a jacket generally continues to decrease, the unjacketed cables that remain continue to age. As they do so, it is increasingly likely that a fault will develop on these cables. It can be particularly troublesome to locate faults on unjacketed cables as normal Time Domain Reflectometry, or radar, based fault location techniques often do not work, due to the corrosion of the neutral wires. While there is no guaranteed action that would result in locating the fault, this paper will outline some advanced methods, based on field experience, that can help when locating these types of faults. This paper was an article presented at NETA in 2017 and will discuss the Impulse Current method, which does not rely on the neutral wires being intact, in both a theoretical and practical light. 

PC software for Circuit breaker analysis 

In some cases, measuring actual current on the primary conductor is not possible and the user may have to measure current on the secondary circuit of a CT. In this case, the MPQ can be programmed to display the actual primary current values instead of the current measured on the CT secondary circuit. This is done by following the steps given below.

Low voltage cable faults are often unstable, so they can only be located when the cable is conducting live voltage. Testing under these conditions is extremely hazardous, so separations filters, as well as constructional safety methods, should be employed at all times.

Low voltage networks are a huge national investment, under daily pressure to give out power for hours at a time to a plethora of electrical appliances. It is therefore essential that their cables and transformers are tested often to prevent outage. To effectively test the components in low voltage networks, it’s important to know the different types of systems within them and how they are structured.

Fault occurrences in medium voltage networks are usually covered by redundancy in the system which, with appropriate switching, usually ensures a relatively uninterrupted continuation of the supply for the customer. A lengthy wait until the fault can be corrected only results in the increased risk of a second failure in this area, creating a customer outage that cannot be restored by switching.