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Industrial Power Systems

Adam [email protected]

SummaryThis project is the design and modification of an industrial plant using SKM Power Tools. The plant losses were finalized at 38kW and 186kVAR. The transformer tap settings have

been adjusted for minimum voltage drop, as well as minimum line losses. The power factor was corrected both at starting and running settings for the induction motors.

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ECE471 Final Report Adam Singer

Summary/Introduction/Body………………………………………………….........................2

Circuit Breaker Schedule…………………………………………………..............................3

LV Fuse Schedule…………………………………………………........................................3

MV PD Schedule…………………………………………………..........................................3

Relay Schedule…………………………………………………............................................4

Transformer Schedule…………………………………………............................................4

Motor Starting Schedule and Analysis……………………………………………………..5-6

1000hp Motor TCC Curve……………………………………………………………………...7

300hp Motor TCC Curve……………………………………………………………………….7

Conclusion………………...……………………………………………………………………..8

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Summary

This project is the design and modification of an industrial plant using SKM Power Tools. The plant losses were finalized at 38kW and 186kVAR. The transformer tap settings have been adjusted for minimum voltage drop, as well as minimum line losses. The power factor was corrected both at starting and running settings for the induction motors.

Introduction:

For Industrial Power Systems (ECE471) at Rose-Hulman Institute of technology, I have been tasked with designing an industrial plant based off of the DuPont plant in Terre Haute, Indiana. The plant is to be fed from a 13.2kV switch with a 20kA fault capacity. The loads are primarily induction motors, ranging from 20hp to 1000hp and running at various voltages. Several of the loads are specified as critical, such as the computer and lighting systems. This project centers around making sure National Electric Code (NEC) standards are met, including percent voltage regulation, ensuring line ampacity exceeds load flow current, and time-current co-ordination of circuit breakers and relays. I have also worked to maximize the power factor and minimize the load flow voltage drop at any given bus.

Body:

To minimize line loss, the motor control centers (MCCs) are placed by averaging the load and distance from a set point on the plant layout. I chose to use the Northwest corner as the reference point for MCC1, and the Northeast corner for MCC2 reference. This was done to ensure the load isn’t too spread out. This means wires are able to be routed in very similar paths without cutting across the center of the plant. All wires were designed to be placed on walls and around doorways. Additionally, MCCs were placed on walls where line-of-sight for each controlled motor is possible. This was also done to give each motor space, so as to reduce clutter. MCC1 is located 33’ east from the Northwest corner of the plant. MCC2 is located 23’ west from the Northeast corner. An added benefit of my design is that, because of the close proximity of motors 4,5,6,7,13,15, and 16 with respect to their MCC (less than 15’ distance), I was able to model the motors as having negligible line loss.

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Figure 1 Circuit Breaker Schedule and Settings

Figure 2 LV Fuse Schedule

Figure 3 MV Circuit Breaker Schedule and Settings

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Figure 4 Relay Schedule and Settings

Figure 5 Transformer Schedule and Settings

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Load Type Rated Voltage

LF Voltage(%)

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1 Induction Motor(500hp)

4.16k 99.69


480 99.69

3 Induction Motor(10hp) 480 99.464 Induction

Motor(150hp)480 99.46

5 Induction Motor(15hp) 480 99.466 Induction Motor(15hp) 480 99.467 Induction Motor(15hp) 480 99.468 Induction Motor(20hp) 480 99.49 Induction Motor(20hp) 480 99.37

10 Induction Motor(20hp) 480 99.3511 Induction Motor(20hp) 208 96.3412 Induction Motor(20hp) 208 96.3413 Induction

Motor(1000hp)4.16k 99.67


480 99.85


480 99.85


480 99.85

17 Induction Motor(75hp) 480 99.7618 Induction Motor(75hp) 480 99.7320 Synchronous

Motor(400hp)4.16k 99.69

Figure 6 Motor LF Voltage

In the table above (figure 6), I have identified each motor load and its load flow voltage as a percent of its rated voltage. No LF voltage exceeds its rated voltage, nor does any load go below the 5% NEC requirement. The lowest margin of compliance is at the 208V critical bus, giving a 1.34% compliance margin.

In order to verify the 10%VD motor starting criteria, I created a worst case scenario in which the 3 most powerful motors on each bus started at the same time.

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From the initial data, I adjusted the starting capacitor bank to account for the increase in VAR consumption. I elected to use 4 capacitor banks in total, 2 for starting PF correction and 2 for running PF correction. I placed 2 at Substation B, as it was the largest consumer of VARs, in addition to 2 at Substation C. This provided the most balanced distribution of VAR production, and allowed me to minimize the number of total banks required. The lowest margin of NEC criteria is at Substation B, the largest power consumer in the plant. The motors are in agreement with NEC criteria by at least 2%.

Load Number

Rating(hp)

%VD When Motor Starts

Substation B

1 500 92.732 500 92.74

13 1000 92.65MCC1

14 300 95.6415 300 95.6416 300 95.64

MCC24 150 96.719 20 96.54

10 20 96.58Critical Bus

23 50 92.7325 20 9311 20 92.15

Figure 7 Motor Starting %Voltage Drop

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Figure 8 13-1000hp Motor TCC

Figure 9 14-300hp Motor TCC

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Conclusion:

The final load flow power factor came out to be 0.98, with a total system loss of (38+j186)kVA. This exceeds the minimum 0.97 utility pf, and is well below my initial prediction of 50kW loss. This was in part due to my assumption that several motors were close enough to their respective busses/MCCs to have negligible kW line losses. The load flow analysis shows a minimum VR of 1.3%, providing a substantial margin of error in the event of plant expansion. The motor starting study concluded that, even if all of the largest motors on each bus started at once, the plant would remain within the NEC required 10% VD, with a minimum of 2.6% compliance margin.

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