Types of tests

As with other power system protection and control devices, PMUs must undertake various types of tests to verify reliable and suitably accurate operation in the installed system. These tests include a thorough conformance test, which typically includes electrical, environmental, mechanical, and performance conformance tests for each new model of PMU. Factory acceptance tests verify that a manufactured product performs as designed. Field acceptance tests (commissioning tests) and periodic maintenance tests verify that PMUs are configured and perform as desired in the particular installation. These tests should follow the requirements and procedures of the relevant international, national and industrial standards, and guidelines where applicable. The application of a PMU has some unique requirements, as follows:

⎯ High accuracy of time synchronization of the measurement results and time tagging ⎯ Unified performance of all PMU units across an installed system

⎯ Interoperability of PMUs and other PMU system components, such as PDCs

These unique requirements demand a comprehensive set of functional performance, conformance, and interoperability tests to be conducted, employing a well-defined test approach to verify that the performance of an installed PMU system can meet its desired objectives and allow products from various vendors to be integrated into the PMU system. The descriptions of different types of tests in this document focus on the conformance and functional performance tests that are unique to PMUs and synchrophasor measurement devices. The conformance tests are designed to verify whether the PMU meets the requirements of IEEE Std C37.118-2005 or IEEE Std C37.118.1-2011, under steady-state, transient, and dynamic power system conditions, and the associated interface requirements as given in IEEE Std C37.118.2-2011 or IEC 61850-90-5. For other standard tests, such as electrical, environmental,

and mechanical tests, please refer to the relevant international, national, and industrial standards and guidelines as listed in Clause 2 and Annex A.

7.3.1 PMU conformance tests

PMU conformance tests will be included in a comprehensive type test program and performed on each new type of PMU devices. A complete set or a subset of conformance tests should also be performed for PMU devices after firmware/software and hardware revisions depending on the extent of the revision. A complete PMU test program will also include electrical, environmental and mechanical tests. Please refer to the relevant international, national, and industrial standards and guidelines, such as IEC 61850-3 or IEEE Std 1613 [B31], for requirements of these tests.

The description of the PMU conformance tests in this guide includes performance and interoperability conformance tests that are unique to PMU and synchrophasor measurement devices. The conformance tests are performed to verify whether a PMU or a synchrophasor measurement device meets the requirements of the relevant standards, e.g., IEEE Std C37.118-2005, IEEE Std C37.118.1-2011, IEEE Std C37.118.2-2011, and IEC 61850-90-5.

7.3.1.1 PMU message protocol conformance test

To verify the interoperability of different PMU models, a message protocol conformance test can be performed to confirm all configuration/command/data frame implementations conform to the relevant standards, e.g., IEEE Std C37.118-2005, IEEE Std C37.118.2-2011, and/or IEC 61850-90-5.

If manufacturer/user custom control/data message frames are defined, they should be verified according to agreements between manufacturers and users.

7.3.1.2 PMU performance conformance test

IEEE Std C37.118-2005 defines the TVE metric and establishes the level 0 and level 1 performance compliance requirements under steady-state conditions. IEEE Std C37.118.1-2011 establishes M-class and P-class performance compliance requirements under steady-state as well as transient and dynamic conditions. Consistent performance among all PMUs in an interconnected system is of great importance for interoperability.

This subclause describes the purpose of each performance conformance test and the requirements of the test. Performance tests are divided into steady-state and dynamic tests, latency, and time quality tests. Steady-state tests are defined as tests where the magnitude and frequency of the test signals do not change during an individual subtest. Otherwise, a test will be considered as a dynamic test.

The steady-state and dynamic test requirements for test signals injected at the PMU’s input terminals are defined by IEEE Std C37.118.1-2011 or IEEE Std C37.118-2005.

7.3.1.2.1 Initial functionality verification

Prior to the full spectrum steady-state tests and/or dynamic tests, a PMU must pass the following basic functionality tests.

7.3.1.2.2 Basic functionality test

The basic functionality of a PMU device must be verified at all reporting rates under the following conditions:

⎯ Pure sinusoidal input signal (THD < 0.1%).

⎯ Input signal frequency at rated 50 Hz and/or 60 Hz system frequency. ⎯ Balanced three-phase input signal.

⎯ Single-phase input signals.

⎯ Input signal is synchronized to produce known phase angles for each reported phasor.

⎯ PMU must report correct phasor values in the preceding tests with TVE less than 1% as specified in IEEE Std C37.118.1-2011. Additionally, the out-of-band interference test should be run to verify the filters at each reporting rate.

Manufacturer-implemented non-standard reporting rates may be verified according to the manufacturer’s own specifications and/or agreement between the manufacturer and users.

7.3.1.2.3 Steady-state performance conformance test

The steady-state performance conformance tests are conducted to confirm that the accuracy of a PMU is within the specified limits when exposed to specified steady-state operating conditions.

The steady-state performance conformance test should be performed according to the signal range and test conditions specified in IEEE Std C37.118.1-2011 Table 3. Additionally this guide presents a test plan for a

phase or magnitude unbalance test.

It is common practice to verify manufacturer-specified steady-state performance of a PMU in extended signal ranges and test conditions according to manufacturer’s own specifications or agreement between the manufacturer and users.

7.3.1.2.4 PMU performance conformance levels

In order for a PMU to conform to IEEE Std C37.118.1-2011, it must be classified by performance class (M or P). The P or M performance level is to be specified for each data reporting rate that a PMU supports. 7.3.1.3 Multifuncation PMU device performance test

When phasor measurement is one of the functions in a multifunction device, the performance test of such devices should also verify the following:

⎯ That operation of other functions will not cause interference, degradation, and disruption of the performance of the PMU function under all operating conditions.

⎯ That the PMU function will not cause interference, degradation, and disruption to the performance of other functions under all operating conditions.

⎯ That the actual range of input signals for a multifuncation PMU is determined by (1) the types of transducers dictated by its primary functions, and (2) the IEEE C37.118 required signal range for phasor measurement.

7.3.1.4 Certification of conformance

Certification of conformance should be issued only to PMUs fully conformed to the requirements of IEEE Std C37.118-2005, IEEE Std C37.118.1-2011, and/or IEEE Std C37.118.2-2011, accompanied by a detailed test report. Both certification of conformance and the test report will declare that all tests were conducted in full compliance with the test requirements and test procedures specified in the standard or proposed standard, and that the tests were performed by qualified test laboratories. The test report must contain a detailed description of each test conducted, test equipment used, test setup description, test conditions, and test results.

7.3.2 Interoperability test

PMUs and all other system components that communicate with each other, such as PDCs from different manufacturers, must conform to the same protocol specified by IEEE Std C37.118.2-2011 or IEC 61850- 90-5 through protocol conformance tests. Protocol conformance is the basis for all system components to be interoperable with each other, but protocol conformance may not be sufficient. To further confirm that PMUs, PDCs, and other system components from different manufacturers can interoperate and work with each other as a system, a set of tests, including performance tests, should be conducted. The tests to show interoperability are in addition to protocol conformance tests conducted for individual PMU, PDC, or other system component. Interoperability tests should confirm that system components work properly together and adhere to performance requirements as required by applications. Tests for interoperability should also be conducted for PMUs, PDCs, and other system components with custom-defined protocols, if any. The tests to demonstrate interoperability may be conducted by a qualified independent test laboratory, or jointly by manufacturers and user representatives. The tests may be performed in a laboratory or field environment.

7.3.3 Factory acceptance test

Each PMU unit passes a proper factory acceptance test program to detect any manufacturing defects, similar to substation protection, control, and networking devices. In addition to electrical, environmental, and mechanical tests, each PMU must be verified in the factory acceptance test that it can:

⎯ Correctly receive the synchronized timing signal according to the specifications (e.g., correct reception of GPS signals under specified signal strength).

⎯ Send/receive configuration/command/data frames according to protocols defined (e.g., send/receive configuration as given in IEEE Std C37.118.2-2011 or initiate an IEC 61850-90-5 frame through a 61850 client).

⎯ Meet phasor measurement performance requirements at a selected set of test conditions within the specifications of IEEE Std C37.118.1-2011.

7.3.4 Field tests

Field tests are conducted to verify the proper functionality of a PMU at its installed location after it has been installed. The field tests include field commissioning tests and periodic maintenance tests.

7.3.4.1 Field commissioning test

As with any other digital IEDs installed in the substations, the PMU field commissioning test must include routine visual inspection, insulation test, wiring check, basic functionality check, etc., as required by the relevant standards, such as 2003 NETA Acceptance Testing Specifications for protection and control equipment.

In addition, a PMU field commissioning test will verify the following: ⎯ Phase A designation verification and confirmation.

⎯ Correct phase sequence verification.

⎯ Correct phasor magnitude measurement verification.

⎯ Correct indication of time synchronization being normal or in a locked or synchronized condition. Also, synchronized timing source verification (e.g., GPS signal strength and reception meet the specification).

⎯ Data and control frames sending/receiving verification.

PMUs are not usually deployed as independent measurement devices. A PMU system typically consists of many PMUs and one or more PDCs. Once a PMU passes the above basic tests and its proper communication with PDCs are established, further system integration tests are conducted as a part of the PMU field commissioning tests. The system integration tests verify the following:

⎯ Proper sending/receiving data/control frames to/from PDCs ⎯ Proper registration of each PMU in the PDC database

⎯ Proper logging of PMU activities, such as on-line/off-line time, setting change, and so on ⎯ PMU status monitoring and trouble reporting

⎯ Proper handling of communications channel problems and PMU malfunctions ⎯ Communications channel throughput and PDC loading levels

7.3.4.2 Periodic maintenance test

Performance of a PMU must be checked periodically to verify that it has not been changed and deteriorated.