Chapter 4: Design of Electrical System4.1 Design methodology

Figure 4.1: Design StrategyThe design of electrical system needs to satisfy multiple constraints such as safety, manufacturability, reliability and economic. In order to satisfy these constraints, there are provisions from different codes and standards that were adopted in the design. For design optimization, there are three computer software that can be used to optimize the design. AutoCAD was used in the design of electrical power distribution system and emergency back-up power system. Solid-works was in the design of lightning protection system and grounding system. EDSA Paladin Design Base was used for simulating the fault conditions at different locations of the power system. The values of fault current were the basis in the design of electrical power system protection.Cable size computation/diameter size computation and ampacities & Short Circuit Analysis for the KAIC rating of CBs

FULL LOAD CURRENT OF MOTORSSection 4.30.2.4 Conductor supplying several motors and other loads shall have an ampacity at least equal to the sum of the full-load current rating of all the motors plus 25 percent of the highest rated motor in the group.Full Load Current: (See table 4.30.14.4 page 424)Motor 1: 20-Hp.54 AmperesMotor 2: 20-Hp.54 AmperesMotor 3: 20-Hp.54 AmperesMotor 4: 5-Hp..15.2 AmperesMotor 5: 5-Hp..15.2 AmperesMotor 6: 5-Hp..15.2 AmperesMotor 7: 5-Hp....9.6 AmperesMotor 8: 5-Hp.9.6 AmperesMotor 9: 5-Hp.9.6 AmperesMotor 10: 5-Hp.9.6 AmperesMotor 11: 5-Hp.9.6 Amperes25% of the largest Motor 54 Amperes x 0.2513.5 Amperes _________________________

Total Current...269.1 Amperes

Main Circuit Breaker: (See table 2.40.16 p. 140)Use: 300 AT, Three-pole ITD Circuit BreakerFeeder Size: (See table 3.10.1.16 p. 299)Use: 3-150mm2 THHNEquipment Grounding: (See table 2.50.6.13 p.196)Use: 1-22mm2 THHNSize of Conduit: (Table 9.1.1.4 p.1235)For THHN-2, 150mm2 = 298.6mm2, 22mm2 = 52.8mm2 (Table 9.1.1.5 p.1240: Dimensions of Insulated Conductors and Fixture Wires)

Use: 65 mm IMC Conduit

1. For Motor-1, Motor-2, Motor-3 Air Blowers (Three 3-phase, 230 volts, 20-Hp motor) Full Load Current: (See table 4.30.14.4 page 424)20-Hp.54 AmperesBranch Circuit Conductor: The feeder conductors for motor loads are sized up according to provision in Article 4.30.2.2(a): Single Motor wherein conductors that supply a single motor used in a continuous duty application shall have an ampacity of not less than 125 percent of the motors full load current rating. The design formula for feeder conductor sizing is

Use: 3-14mm2 THHN (See table 3.10.1.16 p. 299)

Motor-Over Load Protection:The fault protection for motor loads are sized up according to Article 4.30.4.2(a)(1). Where motor is protected by a separate overload device, the motors are required to have a overload protection rated or set to trip at not more than 125% of the full-load current. The design formula for over load protection conductor sizing is

Use: 67.5 Ampere(Maximum) [See Section 4.30.3.2(a)]

Branch Circuit Short-Circuit and Ground Fault Protection: (See table 4.30.14.6)The fault protection for motor loads are sized up according Article 4.30.4.2(a)(1): Motor and Branch-Circuit Overload Protection wherein the motor branch-circuit short-circuit and ground fault protective device shall comply with Table 4.30.14.6, p626: Maximum Rating or Setting of Motor Branch-Circuit Short-Circuit and Ground-Fault Protective Devices. Formula for sizing fault protection is Inverse Time Delay:

Use: 150 AT, Three-pole ITD Circuit Breaker (See table 2.40.16 p. 140)

Equipment Grounding: (See table 2.50.6.13 p.196)Use: 1-14mm2 THHN

Size of Conduit: (Table 9.1.1.4 p.1235)For THHN-2, 14mm2 = 33.2mm2, 14mm2 = 33.2mm2 (Table 9.1.1.5 p.1240: Dimensions of Insulated Conductors and Fixture Wires)

Use: 20 mm IMC Conduit

2. For Motor-4, Motor-5, Motor-6 Pumps (Three 3-phase, 230 volts, 5-Hp motor) Full Load Current: (See table 4.30.14.4 page 424)20-Hp.15.2 AmperesBranch Circuit Conductor:

Use: 3-3.5mm2 THHN (See table 3.10.1.16 p. 299)

Motor-Over Load Protection:

Use: 19 Ampere(Maximum) [See Section 4.30.3.2(a)]

Branch Circuit Short-Circuit and Ground Fault Protection: (See table 4.30.14.6)

Use: 40 AT, Three-pole ITD Circuit Breaker (See table 2.40.16 p. 140)

Equipment Grounding: (See table 2.50.6.13 p.196)Use: 1-5.5mm2 THHNSize of Conduit: (Table 9.1.1.4 p.1235)For THHN-2, 3.5mm2 = 8.6mm2, 5.5mm2 = 13.9mm2 (Table 9.1.1.5 p.1239: Dimensions of Insulated Conductors and Fixture Wires)

Use: 15 mm IMC Conduit3. For Motor-7, Motor-8, Motor-9, Motor 10 and Motor 11 Pumps (Three 3-phase, 230 volts, 3-Hp motor) Full Load Current: (See table 4.30.14.4 page 424)20-Hp.9.6 AmperesBranch Circuit Conductor:

Use: 3-3.5mm2 THHN (See table 3.10.1.16 p. 299)

Motor-Over Load Protection:

Use: 12 Ampere(Maximum) [See Section 4.30.3.2(a)]

Branch Circuit Short-Circuit and Ground Fault Protection: (See table 4.30.14.6)

Use: 30 AT, Three-pole ITD Circuit Breaker (See table 2.40.16 p. 140)

Equipment Grounding: (See table 2.50.6.13 p.196)Use: 1-5.5mm2 THHNSize of Conduit: (Table 9.1.1.4 p.1235)For THHN-2, 3.5mm2 = 8.6mm2, 5.5mm2 = 13.9mm2 (Table 9.1.1.5 p.1239: Dimensions of Insulated Conductors and Fixture Wires)

Use: 15 mm IMC Conduit

Motor LoadsMotor-1 Air Blower: Three 3-phase, 230 volts, 20-Hp motor Motor-2 Air Blower: Three 3-phase, 230 volts, 20-Hp motor Motor-3 Air Blower: Three 3-phase, 230 volts, 20-Hp motor Motor-4 Transfer Pump: Three 3-phase, 230 volts, 5-Hp motorMotor-5 Feed Pump: Three 3-phase, 230 volts, 5-Hp motorMotor-6 Feed Pump: Three 3-phase, 230 volts, 5-Hp motorMotor-7 Decant Pump: Three 3-phase, 230 volts, 3-Hp motorMotor-8 Decant Pump: Three 3-phase, 230 volts, 3-Hp motorMotor-9 Sludge Reduction Pump: Three 3-phase, 230 volts, 3-Hp motorMotor-10 Sludge Reduction Pump: Three 3-phase, 230 volts, 3-Hp motorMotor-11 Sludge Reduction Pump: Three 3-phase, 230 volts, 3-Hp motor