35 kV and Below INTERCONNECTION REQUIREMENTS - BC Hydro

More documents

Recommendations

Info

3.2 Power Quality Revision Date: May 2010 35 kV and Below Interconnection Requirements for Power Generators The operation of the PG's generator(s) should not degrade the quality of electricity in the BCH system. 3.2.1 Power Parameter Information System For PG plant ratings ≥ 1.0 MVA, BC Hydro requires a Power Parameter Information System (PPIS) to ensure power quality is maintained for on-line, off-line, steady and dynamic states. The PPIS is capable of high-speed sampling to capture information such as harmonics, and voltage and current levels. The information captured will allow BC Hydro and PG staff to assess the condition of electricity generating from the PG's facility. BC Hydro will provide the system's requirements, including approved measurement devices (e.g. Power Measurement ION 7650) to the PG. The PG will supply, install and commission the PPIS at the PG's expense. If requested, BCH will perform these services at the PG's cost. See Appendix D for details on the PPIS. 3.2.2 Voltage Fluctuations and Flicker Voltage flicker is an increase or decrease in voltage over a short period of time, often associated with motor starting or fluctuating load. The characteristics of a particular flicker problem depend on the characteristics of the load change and the fault level at the point-of-common coupling. A voltage flicker problem may occur in the BCH distribution system when: (a) An induction generator is started and accelerated as a motor. (b) An induction generator is connected to or disconnected from the BCH system. (c) A PG interconnected at primary voltage normally energizes the PG entrance transformer from the BCH feeder. In cases where the entrance transformer is large and the BCH fault level is low at the POI, the PG may be required to energize the entrance transformer from the generator. A PG switchyard design, which taps the station service ahead of the PG entrance CB, provides PG startup power with PG entrance CB open. (d) When a large synchronous generator sheds or makes a significant block of load. All PGs should take steps to minimize flicker problems from their generator(s). The standards for voltage flicker at the Point-of-Interconnection of a PG with BCH are as follows: Number of Times Permitted Voltage Change Not to Exceed +/-3.3% of normal voltage once per hour in urban systems supplying many customers +/-6.5% of normal voltage once per hour in rural systems supplying few customers Voltage dips exceeding 6.5% but not exceeding 9% may be permitted by BCH at predetermined times that are acceptable to BCH. Voltage dips more frequent than once per hour must be limited to the “Border Line of Irritation Curve” contained in Appendix G, Permissible Voltage Dips – Borderline of Irritation Curve. 12
3.2.3 Voltage and Current Harmonics Revision Date: May 2010 35 kV and Below Interconnection Requirements for Power Generators Harmonics can cause telecommunication interference and thermal heating in transformers. They can disable solid state equipment and create resonant overvoltages. In order to protect equipment from damage, harmonics must be managed and mitigated. The harmonic content of the voltage and current waveforms produced by the PG should be restricted to levels which will not cause interference or equipment operating problems for BCH, its customers or telephone communication circuits. Generator auxiliary equipment, such as variable speed motor drives, are more likely to introduce harmonics into the distribution system than synchronous generators. Single frequency and total harmonic distortion measurements may be conducted at the Point-of- Interconnection, PG site, or other locations on the BCH system to determine whether the PG’s equipment is the source of excessive harmonics. The introduction of harmonics in the BCH system shall not exceed the following: (a) In order to compare levels of harmonic distortion in a power system, the Total Harmonic Distortion (THD) is used, defined as the ratio of the RMS value of the harmonic to the RMS value of the fundamental voltage or current. BCH follows the IEEE Standard 519-1992, "IEEE Recommended Practices and Requirements for Harmonic Control in Electric Power Systems". Section 10 describes the current distortion limits that apply to individual consumers of electrical energy. Table 10.3 lists the current distortion limits for distribution systems 120 V through 69,000 V. Consumers with power generation equipment must limit Total Demand Distortion (TDD) to 5.0% at the point of common coupling (within an industrial plant, the point between the non-linear load and other loads). TDD is harmonic current distortion in % of maximum demand load current over 15 or 30 minutes. Section 11 in IEEE 519 describes the quality of electrical power that the utility should provide the consumer. Table 11.1 lists a maximum total harmonic voltage distortion of 5.0% at the point of common coupling for systems 69 kV and below, with individual harmonic voltage distortion not to exceed 3.0%. (b) Harmonic-caused telephone interference problems have limited correlation with I•T products. This guide imposes no design limits on the calculated I•T values. I•T denotes the inductive influence expressed as the product of the rms value of the current waveform (I) and the telephone influence factor (TIF) of the current waveform (T). TIF was developed to account for the frequency response characteristics of the coupling between the powerline and the telephone lines, the telephone system, and the human ear. Telephone interference is, in many cases, caused by residual (zero sequence) harmonic currents. Also, indirect harmonic telephone interference may be caused by the interaction of non-residual harmonic currents with the supply system equipment. Since the indirect interference is impossible to predict in most cases, applying I•T limits, balanced or residual, serves little useful purpose. Although no design limits are imposed, harmonic-telephone interference can be checked using measurement techniques. Telephone interference due to harmonics involves three major factors: the existence of the source of interference, the coupling between the source and telephone cable, and the susceptibility of telephone equipment. The I•T product only addresses the problem of the source of interference. The complexity of harmonic-telephone interference makes it impossible to accurately calculate the interference level with all three factors included. However, telephone interference measurements can be performed on any telephone set vulnerable to generator-induced harmonics, using indices adopted by the telecommunication industry. These measurements are the noise to ground and cable balance. 13
Page 1 and 2: 35 kV and Below INTERCONNECTION REQ
Page 3 and 4: Revision Date: May 2010 35 kV and B
Page 5 and 6: 1. INTRODUCTION 1.1 Scope Revision
Page 11: Revision Date: May 2010 35 kV and B
Page 27 and 28: Table 2: Response to Abnormal Volta
Page 35 and 36: 8.6 Apparatus Revision Date: May 20
Page 37 and 38: APPENDIX A DEFINITIONS Revision Dat
Page 45 and 46: 35 kV and Below Interconnection Req

35 kV and Below INTERCONNECTION REQUIREMENTS - BC Hydro

Create successful ePaper yourself

Delete template?

Save as template?