The ANSI / IEEE set

The ANSI / IEEE set designs a substation to the ANSI standards and the standards of the Institute of Electrical and Electronics Engineers (IEEE), with the National Electrical Safety Code (NESC). The Standards input selects it for the project. The set takes its yard clearances, its ring bus and its station service from RUS Bulletin 1724E-300, the design guide for rural substations of the Rural Utilities Service (RUS).

Read first: The IEC + CEA / CBIP set

1Standards per design stepCopy link to Standards per design step

the table lists the standards the design follows at each step of the set. The earth mat's method, IEEE Std 80-2013, and the rolling sphere of IEEE Std 998-2012 are the same as in the IEC + CEA / CBIP set (The IEC + CEA / CBIP set). The materials, the body weight, the clearances and the short-circuit method are the set's own.

2Voltage levels and system frequencyCopy link to Voltage levels and system frequency

The set designs pooling substations at 69 kV, 115 kV, 138 kV, 161 kV, 230 kV and 345 kV, with a 34.5 kV collector bus. The frequency is 60 Hz. The rated maximum voltage and the BIL of a level are those of IEEE C37.04-2018 Table 6. The design fault level is one of the rated short-circuit currents that Tables 12 and 16 list at the level. Its rated duration is 2 s below 100 kV and 1 s at 100 kV and above.

the table lists the switching substations of the set. The 345/230 kV substation takes a one-and-a-half breaker scheme on its 230 kV side. The transformers of a switching substation at 230 kV and 345 kV are autotransformers with a 13.8 kV tertiary.

3Short-circuit dutyCopy link to Short-circuit duty

The short-circuit study follows IEEE C37.010-2016 with the breaker capability of IEEE C37.04-2018. It uses the E/X method with adjustment for the AC and DC decrements (§5.2.3), with E/Z in place of E/X, since the neutral grounding resistor is a resistance (§5.2.1). The voltage E is the highest typical operating voltage at the breaker (§5.1.2), and the design takes the level's system maximum voltage. The network is the one the IEC study uses, without the voltage factor c and the impedance corrections of IEC 60909-0.

The X/R ratio comes from separate reductions of the reactances and the resistances (IEEE C37.010-2016 §5.2.3). Above the rated DC time constant of 45 ms (§5.1.4), the current is multiplied by a duty factor (§5.2.2). The factor uses the breaker's asymmetrical capability at the contact parting time (IEEE C37.04-2018 §5.6.2.2, Eq. 1). That time is half a cycle of relay time plus the breaker's minimum opening time (IEEE C37.04-2018 §5.10.3).

The design checks the interrupting duty for three-phase and line-to-ground faults against the rated short-circuit current. It checks the closing and latching current against 2.6 times the rated short-circuit current at 60 Hz (IEEE C37.04-2018 §5.6.2.3). It checks the short-time current for the rated duration, and the DC time constant against 120 ms, the limit of the derating method (IEEE C37.010-2016 §4.11.3.6).

4Yard clearances and the NESCCopy link to Yard clearances and the NESC

The yard's clearances are the row of RUS Bulletin 1724E-300 Table 4-7 for the level's BIL. The clearance to grounded parts is the phase-to-ground check, the metal-to-metal clearance the phase-to-phase checks, and the conductor above grade the ground check. The phase spacing is the larger of the rigid-bus spacing and the switch spacing for horizontal-break disconnect switches in the same bulletin. The yard's bay width and heights are derived from these clearances.

The set has no sectional clearance. The NESC rules take its place. Rule 124A1 sets the clearance of live parts above surfaces where people stand, by the level's BIL (Table 124-1). The design places the bottom of insulators 2.6 m above grade, after Rule 124A3. Rule 110A1 asks for a fence of at least 2.13 m, and the design's fence is 2.44 m. Rule 110A2 keeps live parts outside the safety clearance zone, dimension R of Table 110-1 by the BIL.

Above 1000 m the clearances of a higher standard BIL apply, by the altitude correction of the RUS bulletin, and the insulation levels are not changed. The 345 kV level takes the last row of Table 4-7 and is designed up to 1000 m.

5GroundingCopy link to Grounding

The ground grid follows IEEE Std 80-2013, as in the IEC + CEA / CBIP set. The conductor is annealed soft-drawn copper with the constants of RUS Bulletin 1724E-300 Table 9-2, and its temperature limit is 1083 °C, the fusing temperature of annealed copper in that table. The size is the smallest of 4/0 AWG and the kcmil sizes up to 1000 kcmil at or above the area of Eq. 37 (Conductor sizing). Copper takes no corrosion allowance.

The verdict takes the tolerable touch and step voltages for a body of 70 kg, and the report prints the 50 kg values for information (Tolerable body current). The mesh spacing search starts at 12.19 m, in steps of 0.61 m, down to 3.05 m (Mesh voltage and touch voltage). The ground rods are copper-clad steel. The grid's resistance is not compared with a 1 Ω limit, and the IS 3043 cross-check is not printed.

6Bus schemes, device numbers and instrument transformersCopy link to Bus schemes, device numbers and instrument transformers

The set adds the ring bus of RUS Bulletin 1724E-300 §4.6.4: a closed loop with a breaker between each two bus sections, each section supplying one circuit (Bus schemes). The ring takes 3 or 4 circuit positions on an AIS yard. A new project takes the ring bus at 69 kV to 161 kV and the one-and-a-half breaker at 230 kV and 345 kV. A ring bus has no bus voltage transformers, so each circuit has its own potential source (§4.6.4).

The SLD numbers devices by function, after IEEE C37.2-1996 as RUS Bulletin 1724E-300 reprints it. A circuit breaker is 52 and a disconnect switch 89. The current transformers, voltage transformers, surge arresters, transformers, reactors and resistors carry their names. A new project's CT secondary is 5 A, with multi-ratio HV CTs, 0.15 class metering cores and C800 relaying cores, and the voltage transformers are 115/√3 V.

The plant's reactive power device is a static synchronous compensator (STATCOM), sized for a power factor of 0.95 at the high side, after FERC Order No. 827. The station service is 480Y/277 V three-phase four-wire (RUS Bulletin 1724E-300 §15.1). The DC system is 125 V with vented lead-calcium cells rated at the 8 h rate (§15.2), and a standby generator with an automatic transfer switch.

7Terms and units of the deliverablesCopy link to Terms and units of the deliverables

The set's drawings, reports, bill of materials and 3D model use inch-pound units and the IEEE terms. Lengths print in feet and inches, and distances in miles, with temperatures in °F. Ground grid conductors are in AWG and kcmil. Masses stay in tonnes, and soil resistivity in Ω·m. The sheets are ANSI D (34 × 22 in) at engineering scales, and the DXF files are in inches. the table lists the terms that change.

The set prints Dyn1 on the station service transformers and YNa0d1 on the autotransformers with a delta tertiary. A standard delta-wye step-down transformer has its high-side voltages leading the low side by 30°. The project's own names, client and people are kept as typed.

8What the set does not offerCopy link to What the set does not offer

The set's levels end at 345 kV. The 500 kV level is not offered, since its BIL is beyond RUS Bulletin 1724E-300 Table 4-7. The 765 kV switching substation is a level of the IEC + CEA / CBIP set only. A 345 kV project above 1000 m is not designed. A generating plant with synchronous generators is designed on the IEC + CEA / CBIP set, since its 11 kV station board is not a level of this set. A ring bus is not designed on a GIS yard, nor with more than 4 circuit positions. The validation names the field and what to choose.

9Compliance checklistsCopy link to Compliance checklists

The set's checklists are NESC and NFPA, IEEE and ANSI, and Interconnection. Their items are numbered NESC-01, IEEE-01 and GRID-01 onwards. An item cites its clause, or its standard alone where it has no clause. The statuses are those of the IEC + CEA / CBIP set's checklists (The IEC + CEA / CBIP set, Compliance checklists).

The NESC and NFPA list holds the NESC clearance, fence and sign rules, the grounding of the NESC, NFPA 70 for the control building, NFPA 780 and NFPA 850. The clearance and fence items are automatic, from the yard's NESC checks. The IEEE and ANSI list holds the IEEE 80 grounding items at 70 kg, the IEEE 998 shielding, the IEEE C37.010 duty, the IEEE C37.04 closing and short-time checks and the DC control range. It also holds IEEE 485, IEEE 946, IEEE C37.13 and IEEE 1818 for the DC system and the station service. The equipment items cite ANSI C84.1, IEEE C57.12.00, IEEE C57.13, IEEE C62.11 and IEEE C62.22. The installation items cite IEEE 693, IEEE 979, IEEE 980 and IEEE 1127.

The Interconnection list holds the power factor of FERC Order No. 827 and the reactive power and ride-through of IEEE 2800-2022. It also holds the ride-through of NERC PRC-024-4 and PRC-029-1, and the harmonic limits of IEEE 519. An item that does not apply to the project's plant reads Not applicable, with the reason.