The scope of this TSS is limited to the testing of PMU electrical performance. As of this revision of the TSS@ the standard for PMU performance is IEC/IEEE Joint Standard 60255-118-1-2018@ IEEE/IEC International Standard?? Measuring relays and protection equipment??Part 118-1: Synchrophasor for power systems??Measurements.1 This TSS will be revised as the standard for PMU performance is revised. Users are encouraged to check for the latest revision of this document. This is the third revision: Version 1 complies with IEEE Std C37.118-2011. Version 2 complies with IEEE Std C37.118.1a-2014. Version 3 complies with IEC/IEEE 60255-118-1-2018. Purpose This test suite specification (TSS) provides organizations that are testing phasor measurement unit (PMU) performance with a suite of test plans in accordance with the Smart Grid Interoperability Panel (SGIP) Interoperability Process Reference Manual (IPRM). This TSS further provides requirements for equipment used for the testing of PMUs@ requirements for the measurements made by PMU test equipment@ and requirements for the reporting of PMU measurements. Test plans and requirements in this TSS are more specific than requirements of the standard for PMU performance. The standard specifies the test signals to be input to a PMU under test as well as the performance limits that must be met by the PMU@ but neither specify the test procedure to be used nor the specific calculations made to determine PMU performance. Without specific test procedures and calculations@ tests that are implemented by different test designers may yield different results. PMU testing organizations that participate in The Institute of Electrical and Electronics Engineers Conformance Assessment Program (ICAP) PMU Conformance Assessment Program must comply with the test plans and requirements in this document. Conformance with this TSS is assessed as part of the ICAP program.