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Describe a Transformer
Delta, 3 loads connected in a triangle
Wye, Y shaped, 3 loads plus a neutral wire which allows single phase power.
Explain the process of selective tripping. Why is it designed within the electrical system? How is it accomplished?
Selective Tripping means that when a fault occurs anywhere in the distribution system, one and only one breaker will trip
The tripped breaker will be upstream from the fault so a chain reaction would be prevented (cascading failure)
trips breaker closest to fault.
type of ups
b. Model, Type, and Capacity
•
Schneider Galaxy VX
•
Double-Conversion
•
1MW
Define and describe the LSIG settings found on the Trip Unit of a circuit breaker.
- Long time setting
Overload Protection
S - Short time setting
Low level fault short circuit protection
I – Instantaneous setting
High level fault short current protection
G - Ground fault setting
Equipment ground fault protection
UPS Alarming set points
Over Temperature
Power module failure
Communcation failure
Inverter/Rectifier failure
Fan failure
Modes of Operation for UPS
On Battery
Normal
Static bypass
Maintenance bypass
Explain the difference between Maintenance Bypass and Static Bypass. Describe in which situations Maintenance Bypass would be required.
Static bypass: for internal faults within the ups. diverts power from rectifier/inverter (internal) automatically/manually transfers load to utility line in case of ups failure or overload.
maintenance bypass: external manual switch that allows UPS to physically bypassed for servicing or replacement without interrupting load.
Which components are fed by ATS’s
Preaction
BMS
Dampers
CRACs
Which component acts as the interface for the PLC
ROP - Remote Operating Panel
Provide an in-depth explanation of the difference between Single-Phase AC power and Three- Phase AC power. Which one do we use for our critical loads and why.
Single-Phase AC power – one sine wave created by one hot wire and one neutral
Three-Phase AC power – three sine waves, 120˚ apart each with one hot wire and one neutral
Critical loads use 3-phase because it’s the most power efficient source
Define the following electrical parameters, to include their base measuring units and symbol.
Voltage: pressure that pushes electrons through circuit; volts V,KV
Current: flow of electrons thru circuit; amps
Resistance: opposes current; ohms
Power: work being done in a circuit; Watts
Frequency - # of times of ac completes full cycle in a second. ; measured in Hertz HZ
Phase - distribution of AC power, single and 3 phase. one hot, one neutral wire single phase.
Describe the importance of PPE in data centers, to include some common PPE equipment worn in the Data Center. What is the first step of donning PPE that is commonly overlooked during electrical maintenance?
PPE - Personal Protection Equipment -
First step for safety is to remove electrically conductive material such as watches, rings, belts with metal, and necklaces. etc...
Provide a general overview on the purpose and function of the PLC as it pertains to the system. In your explanation, be sure to include:
PLC - Programmable Logic Controller
Monitors inputs/outputs, makes decisions to control output devices
Provide a general overview on the purpose and function of an MFR as it pertains to the electrical distribution system. In your explanation, be sure to include:
- Brand
- where are they located
- parameters they are sensing
MFR – Multi-functional Relay
programmed to perform various functions like flashing, timing, or acting as a switch-on/off relay, offering flexibility and cost-effectiveness for controlling electrical circuits
Brand: SEL751
Located: above utility and gen breakers in electrical rooms
parameters watched: voltage, frequency, in-phase
Electrical explosion. Trip settings determine the ARC Flash label.
How MFRs and PLC work together to provide protection to the electrical system in the event of harmful power conditions
MFRs monitor and retrieve data. communicates this info to the PLC.
PLC takes the info and makes automatic decisions based on this data. Has preset logic on the PLC.
Normal Seeking vs Power Seeking; how each returns to primary source of power
Normal seeking – has a preferred power source. Automatically transfers back to preferred.
Power seeking – no preferred power source, stays on current source. Must be manually switched back to primary source.
Define and describe a Circuit Breaker, to include
Controls the flow of the electricity, trips the breaker if there's a fault in the circuit (overload typically)
Manual control to close/open breaker in case of any maintenance or repairs being done.
BREAKER STATUS
Charged
Not Charged
Open
Closed
Tripped
Detail the general loads carried by the following panels in our electrical system:
GPNL: CRACs for UPS, TX for GPNL2, GEN-Mini panel
GPNL2: Preaction, Humidifiers, Dampers, Lights, Receptacles, Exhaust fans
SW-MECH: CRACs, XDMs, MAUs
UPNL: ROP, LFACP, BMS, Security Cabinets
UP-MECH: ATS's for XDM Pumps
Describe LOTO, to include:
a. Purpose
to prevent injuries to workers by ensuring machines and equipment are safely shut down and de-energized before maintenance or repair work begins, preventing accidental startup or release of hazardous energy
b. Basic procedure
Notify all staff of equipment status and work being done
Shut down equipment
Isolate the equipment from hazardous energy
Apply LOTO devices
Verify that the equipment is isolated
c. Location of LOTO policy
Operations guide
Define and describe a Circuit Breaker, to include:
LOTO
Status
Positions
Manual push buttons
Charging handle
Trip unit
Define an ATS. Explain its function in detail
ATS – automatic transfer switch
A device that automatically transfers power from primary source to the secondary source if there’s a failure or power outage
PLC TIMING
1 SEC - Primary Gen Source Available
2 SEC - Critical Voltage Failure (utility to gen)
1 SEC - Undervoltage, (utility and gen), open transition
30 sec - Gen failed to start
5 minute - Gen cooldown
30 minutes - Utility restoration
Explain the meaning and function of an SPD.
SPD - Surge Protection Device
Used to protect equipment from the electrical power surges.
3 SPDs in electrical line up:
1 above switchgear, 1 aboue ups, 1 in GCB