IEEE C57.13.6-2005 pdf free downkload – IEEE Standard for High-Accuracy Instrument Transformers.
This standard defines one new 0.15 accuracy class for voltage transformers, two new 0.15 accuracy classes for current transformers, two new current transformer burdens, and two new current transformer routine accuracy test methods.
These supplement IEEE Std C57.13™ 1 . The new burdens shall be considered for use when current transformers are to be used with electronic meters, and the total in-circuit burden will be less than B-0.1 (2.5 VA at 5 A, 0.9 power factor) defined in IEEE Std C57.13. The new accuracy classes, 0.15 and 0.15S, are available to complement the capabilities of solid state electricity metering of equipment associated with the generation, transmission, and distribution of alternating current. There are two important differences about these new accuracy class definitions as they apply to routine current transformer test requirements:
A low current test is required at 5% of rated current (0.25 A secondary), in lieu of the 10% of rated current test specified in IEEE Std C57.13. This test point corresponds with the light load test point of transformer rated electromechanical and solid state electricity meters as specified in ANSI C12.20.
Routine testing for current transformers certified to meet 0.15 or 0.15S accuracy must include accuracy reading(s) using new burden definition E-0.04. The intent of burden E-0.04 (1.0 VA at 5 A, unity power factor) is to approximate the lowest secondary circuit burden that can occur in practical applications. Testing a current transformer at this burden is analogous to the routine no-load voltage transformer test required by IEEE Std C57.13.
Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments or corrigenda) applies.
5. Basis for standard burdens for use with electronic meters and relays
Electronic meters, relays, and connecting circuits may present a lower burden or lower burden phase angle to the socondary of the current transfomer than standard burdens defined in IEEE Std C57.13. An instrument transformer meeting a given accuracy class at burden B0.1 may not meet the same accuracy class when the application calls for a burden power factor between 0.9 and unily, and or less than 2.5 VA (ats A). Two standard ‘E burdens for ument trunsformers with 5 A rmated secondary are defined in Table 2. These may be used with, or in addition 10, burdens and aceuracy clases delfined in IEEE Std C57.13.
6. Nameplates
Accuracy rating on the nameplate of a current transformer or voltage transformer shall include, as a minimum, the following (see 6.1 and 6.2):
6.1 Current transformer
The standard burdens at which the transformer is rated 0.15 or 0.15S accuracy class.
6.2 Voltage transformer
The standard burdens at which the transformer is rated 0.15 accuracy class.
7. Routine accuracy tests
7.1 Current transformers
Accuracy tests for current transformers with 0.15 or 0.15S metering accuracy ratings shall be made on each transformer when energized at rated frequency. Two or four test points defined in Table 3 may be required.
Test points 1, 2, 3, and 4 in Table 3 are generally required for 0.15 and 0.15S accuracy class transformers.
Ratio and phase angle readings must meet the limits specified in Table 1 for the stated accuracy class.
A transformer may be certified to 0.15 or 0.15S accuracy when it can be demonstrated to inherently meet the limits specified in Table 1 for the stated accuracy class using only test point 1 and test point 2.IEEE C57.13.6 pdf download.