ELE 148 Power Distribution

midterm

Lithium Batteries Parameters?

3.8 - 4.0 V per cell

8 Year life span

Can withstand 150°-250° F

Becoming more popular

VRLA (Valve Regulated Lead Acid) Batteries Parameters?

1.8-2.0 V per cell

77° F optimal temperature

4-5 year life span

Most common + and - plate: Lead plate

5 types of UPS

1) Stand By UPS

2) Line Interactive UPS

3) Double Conversion UPS

4) Delta Conversion UPS

5) Flywheel UPS

What are the two types of Flywheel UPS’

RUPS and DRUPS

Six parts of a UPS?

1) Intelligence Module (IM)

2) Power Module (PM)

3) Batteries

4) Control and Communication

5) Transfer Switch (Static Switch)

6) 3 Important Breakers - B.I.B. M.I.B. M.B.B.

3 Important UPS Breakers?

B.I.B. - Bypass Isolation Breaker

M.I.B. - Maintenance Isolation Breaker

M.B.B. - Maintenance Bypass Breaker

What is Double Conversion?

Incoming AC power is converted to DC through the rectifier which charges the batteries, then gets converted back to AC through the inverter to power the load. The load always runs off the inverter, giving zero transfer time during an outage.

What is Delta Conversion?

Most of the power flows directly from utility AC to the load, with only a small portion processed through the inverter to correct power quality. It's more efficient than double conversion but offers slightly less isolation from utility power.

What is a Single Phase Transformer?

This transformer has one primary and one secondary winding, used to step voltage up or down for a single AC circuit. It's common in residential applications, like the pole transformer stepping utility voltage down to 120/240V for your home.

What is a Three Phase Transformer?

This transformer has three sets of windings (one per phase: A, B, C) and is used in industrial and commercial power distribution. It can be wired in either a Wye or Delta configuration on each side.

In typical power distribution, what are the four most common voltage sources?

1) Main Utility

2) Backup Generators

3) Transition Backup - Batteries

4) On board capacitors

Four main types of 3 phase transformer configurations?

1) Delta Delta (Δ-Δ)

2) Delta Wye - (Δ-Y) Most commonly used

3) Wye Delta (Y-Δ)

4) Wye Wye (Y-Y)

Stand-by UPS

Load will be on inverter only when source power is lost. Inverter will be off or idle during normal operation.

Line Interactive UPS

Same as standby but also switches to inverter when power quality is poor (sags, surges). Load will be on inverter only when source power is lost or source power quality is low.

Double Conversion “on-line” UPS

Load will always be on inverter. Very efficient design which takes “dirty” power and cleans it. Inverter receives DC voltage directly from DC bus to charge batteries. AC→DC→AC

Delta UPS

Very high power, high efficiency UPS design made by Delta Electronics. Has 3 modes - Normal Mode (full double conversion), Delta Mode (cost saving), and Power Loss Mode (double conversion as well).

Flywheel UPS

Used for high power applications greater than 2 Mega Watts. Used for mechanical loads and in sensitive applications where batteries can’t be used. Operate with a high inertia wheel that is hard to turn and stop.

What are the two types of loads in a data center?

Mechanical (pumps and fans) and Critical (IT and fire systems) loads. Critical loads must be battery backed up.

Name the 5 major parts of an Air Circuit Breaker (ACB)

Charging Unit — A spring-charging mechanism that stores mechanical energy to ensure the contacts fully close without arcing. It can be charged manually via a charge handle or remotely via a motor.

3 Contacts — Three sets of contacts (main, arcing, and secondary) separated by an air gap when open to prevent arcing. When the breaker closes, the contacts touch to complete the circuit.

Trip Unit — An electronic or electromechanical unit that governs the breaker's protective tripping behavior using LSIG (Long-time, Short-time, Instantaneous, Ground fault) settings.

Control Unit — Contains two solenoids (open and close) that operate the breaker based on external signals from a PLC, which receives inputs from protection relays to respond to overcurrent, undercurrent, or voltage events.

Communication Unit — Interfaces the ACB with an EPMS or BMS to report status and receive commands, typically communicating over Ethernet/IP or Modbus protocols.

List and name all 10 important ANSI device numbers

25 - Sync Device

27 Undervoltage Relay

47 - Phase Balance Voltage Relay

50 - Instantaneous Overcurrent Relay

51 - AC Time Overcurrent Relay

59 - Overvoltage Relay

74 - Alarm Relay

81 - Frequency Relay

86 - LOTO Relay

87 - Differential Protective Relay

What are the 4 main automation systems in a data center?

Medium Voltage Control System

COP
Back feed Isolation

Dynamic Load Balancing

L in LSIG?

Long time: Helps protect against currents slightly over the breaker’s rating.

Has two settings: times (1.1-1.8x the breaker’s rating) and time (1-30 seconds)

S in LSIG?

Short time: Protects against high short circuit currents that are higher than the long time setting is set to.

There are two settings: times (1.9-5x the breaker’s rating) and time (.1-1 second)

I in LSIG?

Instantaneous: Protects against high current draw short circuit faults.

There is only 1 setting: times (5.1x-20x the breaker’s rating)

G in LSIG?

Ground: Protects against ground fault currents that could cause arcing ground faults or equipment damage.

There are two settings for this: times (.1-.6x the breaker’s rating) and time (.1-.6 seconds)

TCC Graph Parts?

Long Time Pickup

Long Time Delay

Short Time Pick Up

Short Time Delay

Instantaneous Value

What is ANSI device number 25?

Sync Device

What is ANSI device number 27?

Undervoltage Relay

What is ANSI device number 47?

Phase Balance Voltage Relay

What is ANSI device number 50?

Instantaneous Overcurrent Relay

What is ANSI device number 51?

AC Time Overcurrent Relay

What is ANSI device number 59?

Overvoltage Relay

What is ANSI device number 74?

Alarm Relay

What is ANSI device number 81?

Frequency Relay

What is ANSI device number 86?

LOTO Relay

What is ANSI device number 87?

Differential Protective Relay

What is coordination?

The proper trip settings in all breakers. The breaker closest to the source will have the largest trip setting and the breaker closest to the load will have the smallest trip setting.