The objective of application certification type tests (also known as functional tests) is to verify the engineering design and performance of the system and its components through simulation of the full range of expected operating conditions. These cases can be in the form of playback of simulation results or real time interactive testing. Typically, the developers run such type tests only on a first production sample if more than one is to be built.
In the case of playback of simulated cases, the tests rely on power system or apparatus modeling, simulation, and tools to demonstrate the security and dependability of the scheme before shipping to the site. Features include comprehensive modeling of the application, standardized test cases, large variety of test cases to exercise design, and simulation of communications and environmental challenges of a field installation. The test personnel document the test cases and results in some detail. For a specialized protection system or critical application, representatives of the end user may witness some or all of the type testing process to learn the system and gain confidence.
In general, component devices of a system under test have been or should be type-tested according to relevant standards for the physical and electrical environment. For example, protective relays are tested according to specified revisions of IEEE Std C37.90TM as well as IEEE Std. such test results are documented separately. These well defined product type tests are not discussed further in this document.
Commissioning tests (at installation site)
The objectives are to determine whether equipment was damaged or changed during shipping and field installation, to ensure that equipment is installed and wired properly, to verify that installers entered appropriate settings and option selections, and to observe interaction with the power apparatus. The test focus shifts from verification of design to verification that the system is working as designed.
The commissioning test objectives are as follows:
a) Install and integrate the system components with the site current transformers (CTs), voltage transformer (VTs), sensors, communications systems, wiring, and auxiliary power supplies.
b) To verify that factory-supplied connections are correct and complete.
c) To ensure each component performs in accordance with vendor specifications and type testing for that component.
d) Test interactions, and overall system performance, with a sampling of test cases across the spectrum of possibilities but not a comprehensive suite as is used for factory type tests.
e) Test the overall scheme by simulating power system events that cannot be generated on demand, using techniques described in this guide. Examples include transient simulation, tests for abnormal conditions, end-to-end testing, and functional testing of applications using IEC 61850.
f) Operate other power apparatus or secondary control systems in the vicinity to show that the system is secure and/or dependable in the face of spurious environmental influences or communications traffic.
g) Verify proper mapping and operation of the protective device with other data/control systems to which it is interconnected.
Periodic maintenance tests
The objective is to detect in-service failures of components, wiring, interfaces, communications, or unwanted changes of setting or configuration.
a) Assume the design requires no additional verification.
b) Test for correctness of wiring or switching configuration that could conceivably have been changed by maintenance elsewhere in the substation, including polarity or phase rotation, and instrument transformer or other interface grounding/earthing.
Periodic testing should focus on carrying out steps that detect most in-service hardware failures and avoid additional testing that tends to re-verify the design, software behavior, or the fundamental installation correctness that were already confirmed. Excessive testing risks accidental introduction of problems and work errors that leave the system unable to protect after the test is complete and the technicians have left the site. This is especially true for invasive testing that calls for taking systems out of service, disconnecting circuits, changing settings, or opening unit cases.
Note that for electromechanical relays, as well as solid-state and microprocessor-based devices, users have been accustomed to re-verify pickup characteristics during each periodic test because some internal failures can change these characteristics. Relay technicians open test switches and apply a large set of boundary tests from a computer-operated test set.
For microprocessor-based devices with self-monitoring and diagnostics, internal failures have different effects, most of which can be observed during normal operation via data communications or front-panel data checking. For example, metered non fault data that the processor communicates or displays can show any measurement error that could influence trip characteristics.
Although settings could be incorrect, they can also be checked via data communications or the panel. The only element of the tripping chain that might need an overt periodic test is the trip contact and circuit to the breaker, and that can sometimes be tested via communications or the relay front panel. Periodic maintenance tests can thus be minimally invasive, and the risk of problems caused by maintenance activity is reduced. If the scheme is designed and installed with this opportunity in mind, the user may be then able to carry out some or all of the periodic checking without entering the substation.
In making efforts to detect every possible failure, the user should balance the risk from a missed element of low failure probability versus the maintenance risk of introducing a disruptive step to check it.
Troubleshooting tests
It is important to emphasize the value of verifying overall system performance following correct as well as incorrect operations by retrieving and analyzing sequence-of-events and oscillographic records captured from various devices and recorders for nearby disturbances. It is also suggested that correct operations also be studied to verify security and quantify nearness to trip. Some key steps in reviewing performance of relay systems after operation include the following:
A )Periodically review the application in light of power system evolution and protection and control system changes.
b) Analyze relay or digital fault recorder (DFR) data from disturbances for which the protection system did or did not operate.
c) Consider correctness of logic, characteristics, and set points.
d) When problems appear, carry out commissioning-like tests to demonstrate continuing suitability or to verify needed changes.
e) Make and verify needed changes to the periodic test procedures.