Test and measurement or T&M

  • Test & Measurement - Work smarter with PAT records programs

    Jim Wallace of Seaward looks at developments in PAT data management software systems

    With a competitive portable appliance testing market forcing all contractors and PAT contractors to work more efficiently, linking the test functions of tester to effective results programs has taken on increased importance.

    Fortunately, advances in portable appliance testing instrumentation and test data management software means that there are now integrated PAT solutions available that meet the needs of all levels of electrical safety testing.

    In very basic terms PAT testers could be regarded simply as test data collection tools that measure and check the safety of electrical appliances. For fully effective risk management programmes and compliance with workplace safety protocols, how this data is acquired, managed and presented takes on even greater importance.

    As a result, considerable work has also gone into the development of PAT record keeping software systems to enable the user to build and maintain computerised records of test results so that the collected data can be interrogated and used to control electrical safety programmes in a professional and orderly manner.

    In addition, the HSE Memorandum of Guidance on the Electricity At Work Regulations 1989 advises records of maintenance and safety test results should be kept throughout the life of the equipment.

    Software controlled safety testing record systems enable ‘real-time’ records to be maintained, which are easily amended and updated. This enables new equipment to be added and the movement of equipment from one location to another to be tracked.
    Programs used for asset management purposes in this way can search through records very easily and display the record details significantly faster than making changes to a manual paper based system – and with reduced chances of mistakes being made.

    Another advantage is the ease with which re-test schedules can be planned. As the re-test periods for individual items could be anything from three months to four years, it is comparatively easy for test situations and work schedules to become unmanageable. It becomes particularly unwieldy to have someone monitoring a paper record system looking for items which may have remained in use beyond their next test date, particularly when large workplaces or testing contracts can include thousands of appliances.

    Now, matching the availability of different testers, a range of results recording programs possess different features and varying levels of sophistication to meet the needs of all types of PAT testing organisations and personnel.

    Manual data entry systems
    In their most basic form, PAT record keeping programs provide database packages capable of storing and presenting large numbers of test records.

    Because most entry-level PAT testers provide simple pass/fail readings and do not have an internal memory for results storage, complementary software programs at this level permit manual entry of results.

    With these systems, once test results have been entered there can be a range of data manipulation options available that allow different test report templates to be produced – for example, as PDF, TIF or jpeg files.

    In addition some of these elementary or basic level programs also allow different reporting options including the presentation of test histories for individual appliances for comparison or trend analysis purposes.

    More elaborate entry level packages also have the ability to link testing carried out to the automatic generation of invoices – including the option to include the costs of any repairs carried out.

    Once testing has been undertaken and all data entered, it is also possible to produce special ‘certificates of testing’ that can be displayed in workplaces to highlight the electrical safety measured undertaken.

    Direct data download
    For those PAT testers equipped with a memory to record results, basic software packages are also available that enable the direct download of test results into database systems.
    Of course one of the most important considerations for users of PAT testers incorporating an internal memory is the compatibility between the test instrument and the PC program. Most software packages are compatible with different safety tester output formats – although as the range of test instruments has increased over the years it is worth checking with the supplier of your preferred results recording program that your tester will be compatible.
    Some of these types of programs allow both manual and direct download input of data and in broad terms provide the same range of test report options and administrative functions as those described earlier.

    However there are some differences that may be attractive to different types of PAT contractor or user: For example some programs enable test results to be downloaded into existing customer or site specific files – while some download programs produce multiple databases with new results listings being created every time a new set of results is entered.

    Uploading test data
    As PAT testers have become more sophisticated, some have the ability to ‘pre-program’ the instrument with a special testcode (a test routine defined by a numeric sequence) at the start of the working day.

    This is referred to as an upload capability and involves the ability to send an appliance number and testcode from PAT records held on a PC program to the instrument. By uploading this information into the tester, re-testing in the field can be speeded up considerably and detailed test histories can be maintained very easily.

    As a result software programs that combine data upload and download features can be used to create fairly sophisticated asset registers for customers, grouping appliances by type or location and helping to track the movement of equipment between departments or different parts of a building.

    Such high level programs also come with a host of other functions and test templates – including the inclusion of ‘view only’ CD files that enable others to have copies of test records from a parent program that can be viewed without having a copy of the original record-keeping program software.

    Other features include sophisticated presentation and reporting options and the ability to link electrical safety testing records with other asset management or maintenance functions - extending the use of these programs for more general facilities management tasks.

    For contractors carrying out PAT testing as part of more general facilities management functions, software programs are available that include the ability to include reports and details of other health and safety related checks on equipment such as emergency lighting, fire alarms and fire extinguishers.

    Networking options have also been developed for these higher level PAT programs - enabling more than one user to access the program at the same time.

    Special programs
    In addition to the range of record keeping database programs a number of special software packages are available to provide specific test management or PAT administrative functions.
    One example is an e-scheduler module that systematically interrogates the PAT test database and automatically identifies when equipment will be overdue for re-test – issuing e-mail alerts to notify customers or departments immediately of all re-test requirements or overdue warnings.

    In this way this special software can be used to highlight and plan re-test schedules, enabling workloads to be managed efficiently. For testers with an upload capability this program can also directly transfer the appropriate test data into test instruments in preparation for on-site testing.

    The system can also be configured to submit formal re-test price quotations with the alerts for a complete test scheduling and costing proposal, boosting repeat business and enhancing the levels of customer support provided.

    Another example of ancillary is special time manager software that provides information on the test activity of individual users and engineers – providing such details as time of test, number of tests undertaken and time between jobs.

    Analysis of such information enables service or contract managers to understand how often testers are being used, identify improvements in staff training and help field staff to test faster and work more efficiently.

    With developments such as these, PAT results recording and data management solutions are available for all organisations involved in portable appliance testing whatever their requirements.

    At all levels PAT record keeping programs provide real practical benefits to contractors – reducing costs, increasing revenue and productivity, improving safety and providing a truly professional approach to test data management that can only help in the long term development of their business.


    Footnote: To help employers learn more about portable appliance testing Seaward has published a free booklet -
    ‘A Common Sense Approach to Electrical Safety in the Workplace’. This describes the importance of implementing inspection and testing measures that are appropriate to the particular working environment and which are in keeping with the specific risks posed. Further details call 0191 586 3511 or visit www.seaward.co.uk

  • Test & measurement - A primary injection primer

    What is primary current injection testing, and what are its applications? What kind of test equipment is needed for primary injection testing, and what features should users expect to find in the latest test sets? The answers to these questions and many more are supplied by Damon Mount of Megger

    Primary current injection testing is most usually associated with high current and high voltage power distribution systems of the type found in an electricity substation, or in a large industrial installation. The principle it is actually very straightforward: a test current is injected into the primary side of a system – which is often but not always some form of protection scheme – to determine how the system behaves at particular levels of current.
    The system under test might, for example, comprise a circuit breaker with an over-current trip relay that operates via a current transformer (CT). By injecting a predetermined current into the circuit breaker, it is possible to determine whether the relay will trip at this current and, if so, how long the current needs to flow before the trip is initiated.

    Something similar, of course, could be achieved by injecting a test current directly into the trip relay – that is, on the secondary side of the CT. This is secondary current injection testing and it is widely used, not least because much lower currents are needed than are typically required for primary injection testing.

    Secondary injection testing is undoubtedly valuable, but it does not check all of the components in the system. In the scenario discussed, it would not, for example, reveal a defective CT. Neither does it truly mimic the operating conditions – the heating effect of the primary current will not be present and, in some types of test, this can significantly affect the results obtained.

    For these reasons, there are many situations where primary injection testing is considered useful if not essential. Because it tends to be somewhat disruptive – the plant under test must be taken out of service and de-energised and then arrangements must be made for the high current connections needed for the test – primary injection is most usually performed as part of the commissioning procedure for new plant or after major modifications have been carried out. In some instances, however, it can also be an invaluable aid to faultfinding.

    Test sets used for primary injection are invariably built specifically for this purpose. Their primary function is to supply a lot of current – tests typically involve injecting currents from 100 A or so up to 20,000 A. Equipment capable of delivering these sorts of currents is never going to be physically small or lightweight, but remarkable strides have been made over recent years in making primary injection test sets more manageable.

    One way this has been achieved is by using modular current sources, so that for lower test currents only one or two sources are needed, but for higher test currents additional current sources can be added. Test sets that adopt this approach are often assembled on wheeled trolleys that can accommodate the control unit plus up to three or four current source modules. This arrangement makes the test sets much easier to handle.

    Test equipment manufacturers have also noted that only a few applications of primary injection testing involve the highest currents – many requirements can be satisfied with test sets rated at no more than 5000 A, which paves the way for smaller mid-range units. In addition, the highest currents are usually only required for a comparatively short time, to test, for example an instantaneous overcurrent relay, so the test sets do not need to be continuously rated for their maximum current output. Once again, this allows size and weight to be reduced.

    Weight and size are not, however, the only areas where progress has been made. Another useful development is the introduction of test sets where the control unit can be connected to the current generator by a comparatively long control cable. This allows the current generator to be placed very close to the equipment under test, thereby minimising the length of the high current test leads needed, which makes testing easier and more practical.

    To ensure versatility, primary injection test sets need to be able to offer options to cope with a wide range of burdens since, if they do not, there is the possibility that they will not be able to deliver the required test current into the impedance presented by the equipment under test plus the test cables. In the best test sets, this issue is addressed by allowing the output voltage of the current generators to be raised at the expense of output current, so that the total power the test set is required to deliver is not increased unduly. This option is particularly valuable when testing CTs, circuit breakers and busbar joints.

    Another option of great value is an integral timer that can be set to inject the test current for an accurately controlled time, preset by the user. This makes it easy to perform complete circuit breaker tripping time tests that encompass both the relay and the CTs, by injecting the actual fault currents. Auxiliary voltage and current measuring inputs facilitate the testing of CTs and good test sets can provide a wide range of data, including impedance, resistance, virtual power, active power, reactive power, and power factor, together, of course, with CT ratio and polarity.

    A fast acting hold feature for the measuring functions, which is provided in conjunction with a “stop” input further enhances usefulness, as it allows readings to be frozen by applying a signal to the stop input. This makes it possible, for example, to record data relating to the exact moment that a protection relay operates during a test. Some instruments, when used for circuit breaker testing, can even be configured to automatically freeze the measurements at the instant the breaker trips without the need to use the stop input.

    A feature that is just starting to become available on the latest primary injection test sets is zero-crossover synchronisation. This ensures that the test current is turned on only at a zero crossing point, which eliminates DC offset effects and also ensures the best possible repeatability for test results.

    One issue that has been perennially troublesome in carrying out primary injection tests has been heating of the equipment under test while setting up and adjusting the test current. This effect has even been known to trip a breaker under test during set up before the test proper has commenced. Work-arounds are available – test engineers can perform the set up very quickly to minimise heating, or they can prevent tripping at least by isolating the trip circuits. Neither of these options is particularly convenient, however.

    Fortunately, there is a better solution, in that test sets are now available with a so-called I/30 function. This, as its name suggests, reduces the programmed current output of the test set by a factor of 30. Since this means that the heating effect is reduced by a factor of 900, test engineers using this function can take as much care and time as they need in setting up the test with absolutely no risk of significant heating. And, when they are ready to start testing, the output current can be returned to normal at the push of a button.

    Some of the principal applications of primary injection testing, including the testing of circuit breakers and CTs, have already been mentioned in this article. Some test sets can, however, also be programmed for more complex functions, such as testing automatic reclosers and sectionalizers.

    Finally, it is worth bearing in mind that the high-capacity current source at the heart of every primary injection test set is also useful in its own right as convenient way of providing current to carry out heat runs on busbars and other types of switchgear assembly, and for testing ground grid installations where the test set is used to inject current between a reference ground and the ground to be tested. Measuring the voltage drop and the percentage of current flowing through the ground grid then enables an accurate assessment to be made of the ground grid’s performance.

    Primary current injection tests are among the most valuable tests that can be carried out on power systems as they take into account the performance of every component and are, therefore, the most reliable way of assessing the performance of the system under real world operating conditions. In the past, however, primary injection testing has been fraught with inconvenience, not least because of the size and weight of the equipment involved, and because of its limited capabilities.

    Fortunately, things have changed and, as we have seen, the latest primary injection test equipment is much more user friendly – and far less back breaking! For all those involved in the commissioning and maintenance of power distribution systems this could, therefore, be a very good time to take a closer look at how primary injection test sets have changed in recent years, and to look again at the benefits that this form of testing undoubtedly offers.

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