By Maryam Khallaghi, OMICRON Australia
Cutting down on the time required for testing directly results in efficiency and cost effectiveness. Saving time not only reduces the costs associated with people and resources, but also on outage instances and durations which result in significant cost saving.
Time optimisation can be achieved in different stages of the testing process:
- Preparation of test plans and automated test points without the need of excessive calculations
- Preparation of asset under test and connection wirings
- Test procedure and ability to perform multiple tests with the same test set and simultaneously on multiple phases
- Obtaining test results, relevant calculations and assessments on-site
- Preparing test reports
Ability to configure test plans in advance enables fast and effective measurements on-site. To save time, test templates should be built for different asset types ahead of time and stored in an easy to access database. With the optional functionality to synchronise test results between all users, accessing and executing test plans and comparing test results with previously performed tests or similar assets is facilitated in a timely manner. Automated test plans can reduce the effort in calculating test points and allow less experienced users to still be able to perform tests within built guidelines and calculations.
One of the most time consuming stages of the test process is the connection of the test leads, especially when connecting at certain heights requires ladders and other equipment such as cherry pickers. Considering all safety aspects, the test persons can spend hours connecting and disconnecting leads to perform different tests using individual test equipment for each test and on different phases. This time can significantly be reduced by utilising test equipment that can perform multiple tests with single connection set up. In cases such as testing transformers or multi tap CTs and VTs, this can be achieved via a switch box which automatically runs the test on different phases or taps consecutively or with novel technology, running the tests on all phases of the transformer simultaneously and as true three phase.
For example, consider and compare the time, effort and number of leads required for making connections at a height on a HV circuit breaker in the conventional way and using innovative technology, CIBANO 500 in Figure 1 and Figure 2.
With the setup shown in Figure 2, all the required tests can be carried out on the circuit breaker with one set up and one test set, CIBANO 500. These tests include:
- Static/contact resistance (µΩ)
- Timing of main and auxiliary contacts
- Different operation (O, C, O-C, CO, O-CO, CO-CO, O-CO-CO,…)
- Undervoltage test
- Coil currents
- Minimum pick-up test
- Motor current analysis
- Contact travel (motion) of main contacts
- Dynamic contact resistance (DRM)
Dynamic resistance measurement is performed simultaneously for all interrupters. The high-current cables on top of the breaker are kept short. This also minimises the measurement interference from inductive coupling. Furthermore, this avoids the possibility of inducing dangerous voltages, which could be sent back to the operator. Inductive loops when using long test leads are reduced. With the remote modules and short leads, the breaker can be left grounded on both sides.
In the following example, we will consider testing a power transformer. Every transformer part including windings, tap changer, bushings, insulation and core can be tested with a single test set, TESTRANO 600. TESTRANO 600, being a true three-phase unit, can significantly reduce the time in testing and perform all tests such as:
- Transformer turns ratio
- Exciting current
- DC winding resistance
- Dynamic resistance
- Short circuit impedance/leakage reactance
- Demagnetisation of transformer core
- Power factor/dissipation factor (with an additional accessory)
Easy connection is established once on the high voltage and low voltage side of the transformer with two specially designed, colour-coded multi-purpose cables to perform various electrical tests.
For on-load tap changer, one additional cable can be wired to automatically switch between different tap positions and records motor current and voltage.
Figure 3 shows the connection for three-phase testing which has the advantage of using one setup to perform various tests, significantly reduced rewiring effort, energisation of all three phases at once, verification of phase-shift of any winding configuration, built in demagnetisation of the transformer after tests, and fully automated control of the tap changer during the test. This can simplify and speed up the test by one third of the time of a single-phase test set, even if a switch box is utilised.
As an example, the outage time difference for a 400KV transformer with 19 taps can be seen in Table 1.
The benefit of this reduced time is not only significant for the total outage time but also important and beneficial to reduce safety hazards for personnel setting up the test. This is more evident when considering their work condition, often in direct heat and physical activity on heights required to make multiple connections. Safety is also better obtained via the need of handling only one device rather than several devices which itself is low in weight. The lower volume and weight also introduces easier handling and cost savings in terms of storage and shipment of test devices to different sites and locations.
In conventional methods, tests would be performed on-site and measurements were noted to take back to the office to calculate and analyse required data. However, if values obtained were found to be out of range, a repetition of the test could be requested. This meant prolonging the outage time and additional efforts for the test crew to go out on-site and duplicate tests which itself would introduce overtime and possible work on the weekends. This resulted in additional costs related to longer outages and higher human resource costs. With intelligent software test results are visualised upon completion of the test on-site and their “pass/fail” assessment are displayed within the table view and can hint towards further investigation if necessary. In addition, a tooltip indicates which test parameters should be investigated.
A graphical display should help obtain detailed information regarding the measured value and its assessment. Thereby, test results and their reference values, for example, nameplate values, can be compared side-by-side in one diagram all while at the site. The graphical comparison function helps assessing the test results, provides further indication regarding the quality of the measured values, and assists in instant decisions whether a test should be redone or is satisfactory. Measurements can even be compared easily with measurement results of a previous test by loading them into the same diagram, for example, using previous test results of the same or similar asset. With the built-in database, trending of results with respective diagrams are also possible, providing even more insight into asset health.
Preparing test reports is considered as one of the most cumbersome tasks after spending hours on-site. Automatically generated reports including all asset-related information and performed tests helps finish the testing process with ease and reliability. This gives a comprehensive overview of the test object, test results and assessment and is not prone to user error in noting down measured values. Reports can be customised to the organisation’s specific needs and be generated in Microsoft Word and as PDF files.
You can decide which parts are included in the test report and provide comments on every test.
Depending on the test, you can choose from different types of result tables and diagrams contained in your test report. Furthermore, company logos, photos and other test results can be incorporated in individualised test reports to issue test reports with ease and high standards. With a uniform software that operates different test equipment, all relevant test results can be easily compiled in one report.
An important aspect of the report is the pass/fail indication. Limit values can be selected according to applicable guidelines or defined based on your individual customised limit profiles.
A real-time overview of the test results is given during the measurement, including a progress update with an indication of any open tasks. An instant “pass/fail” assessment of the test results is displayed and recorded in the report based on specified limit values.
Commissioning and testing engineers are always under time pressure. Equipment availability is paramount to keeping time schedules, therefore, test sets used must be extremely reliable and robust.
Small and lightweight equipment enables safer handling and reduces costs associated with shipment and storage. The test sets must provide perfect “ad hoc” and manual testing means, thus allowing fast reaction to constantly changing testing requirements, troubleshooting and, and time-saving. Test automation for standard test procedures is a must in order to keep deadlines and achieve time efficiency.
With easy to use equipment and processes like those mentioned above and reduced times for performing different tests, commissioning and maintenance testing activities can be better planned, combined and synergised to reduce the huge volume of system access requests.
Performing tests in an optimised manner reduces outage times and further waste of resources’ time and efforts. It not only saves time and costs but increases safety, reliability and efficiency in line with the mission and values of the power industry.
This partner content was brought to you by Omicron. For more information, please visit https://www.omicronenergy.com/en/product-overview/