IAD51 Qualcards - Full Electrical

Voltage at Utility

230 kV

Voltage at Substation

34.5 kV

Voltage at Step-down transformer

480 V

What does a VISTA do?

VISTA is a manual transfer switch that is fed from two separate substations and can be switched between the two.

Generator Function

Provide backup power if the utility source is unavailable

480/277 Volts

high voltage range, 480 V is between 2 phases, and 277 V is between any phase and neutral.

Normal Status of Generator Breaker

Open

Normal Status of Utility Breaker

Closed

Major components in Electrical Flow path

Utility, Substation, VISTA, Transformer, Switchgear, UPS, PDU, RPP, racks.

IAD51 Electrical Redundancy

Distributive Redundancy - upon loss of 1 line, the other 4 UPS should pick up the remaining.

At what level does load shedding occur?

At the rack level.

Type of Batteries used in our UPS Electrical Rooms?

Lithium-ion Batteries

How many batteries per string in UPS Electrical Rooms

17 Batteries per String

How many strings of batteries?

5 Strings of batteries

How long can we keep load on batteries if loaded to full design?

5-7 minutes

What is the float voltage of the batteries?

570 V

Why do we keep a float voltage of 570 V?

The float voltage is maintained to prevent overcharging.

Voltage

Pressure that pushes electrons through the circuit; measured in Volts

Current

Flow of electrons through the circuit; measured in Amps

Resistance

Opposition to current flow; measured in Ohms

Power

Work done in a circuit; measured in Watts

Frequency

The number of times AC completes a full cycle in a given time period, usually 1 second; Measured in Hertz.

Phase

Distribution of AC power, a single-phase being one hot and one neutral. Position of a wave form at a fraction of a time period

What is AC Power?

Alternating Current, looks like a sine wave. Very good for doing work, present in pretty much every system in the data center.

What is DC power?

Direct current, no change in polarity. Used in batteries and some control circuits.

Single Phase

One Sine wave created by one hot wire and one neutral; Typically used residentially.

3 Phase

3 Sine waves each set 120 degrees apart each one with two hot wires. Most critical loads use this as it’s the most power efficient source.

Power Usage Effectiveness (PUE)

Measures the energy efficiency of a data center, ratio of the total amount of energy used by the building to the energy delivered to computing equipment. Goal is to be as close to 1.0 as possible.

PUE Formula

Total Facility Load / Total IT Load.

Primary Function of a Circuit Breaker

Control the flow of electricity in a circuit

Secondary Function of a Circuit Breaker

Provides Overload Protection by tripping

Major External Components of a Circuit Breaker

LOTO, Status, Position, Manual Push Buttons, Charging Handle, Trip Unit

LOTO Function

Safety measure to ensure equipment is safely shutdown and isolated

Breaker Status

Open, Closed, Tripped, Charged, Not Charged

Breaker Position

Racked-in, test, disconnected, racked-out (withdrawn)

Breaker Manual Push Buttons

Used to manually close/open the circuit

Breaker Charging Handle

When in open status, this charges the spring so the breaker may close

Breaker Trip Unit

Part that opens the contacts of a breaker in the event of a fault

Breaker Status - Open

Circuit is open and there is no power through the circuit

Breaker Status - Closed

Circuit is closed and there is power through the circuit

Breaker Status - Tripped

Fault in the circuit and the circuit has tripped open

Breaker Status - Charged

Ready to close the breaker

Breaker Status - Not Charged

Not ready to close the breaker

What does it mean when a breaker is tripped?

There is an excess of electrical current in the circuit

LSIG

Type of circuit protection and the available adjustments based on certain trip units

L in LSIG

Long time setting; Overload Protection

S in LSIG

Short time setting; Low level fault short circuit protection

I in LSIG

Instantaneous Setting; High level fault short circuit protection

G in LSIG

Ground Fault setting; equipment ground fault protection

Which breaker trips are safe to reset without a thorough breaker inspection?

Engineering team can reset long term setting if they know what caused the trip

Who resets other types of breaker trips?

Any trips besides a long term trip (in some cases) require a technician

Arc Flash

Light and heat created from an arc fault explosion

Why are arc flashes dangerous?

Temperatures can reach 5,000 to 35,000 degrees Fahrenheit.

When are arc flashes most likely to occur?

When preforming energized electrical maintenance and when closing a live circuit breaker

What are the boundaries called for arc flashes? (In order from closest to electrical equipment to farthest)

Restricted Approach Boundary, Limited Approach Boundary, Arc Flash Boundary

What are the spaces called when in comes to arc flashes and the limits? (Closest to farthest)

Restricted Space, Limited Space, then unnamed space

How are trip settings and arc flash labels related?

Arc flash ratings are determined by the trip settings. If settings have changed then the arc flash labels must be updated.

What is Selective Tripping?

It is the process for when a fault occurs anywhere in the electrical distribution system, one and only one breaker will trip. The breaker is usually the one closest to the fault

Why does selective tripping trip the closest breaker upstream?

It trips the closest breaker upstream from the fault as to prevent cascading failure.

How is selective tripping accomplished?

The opening times are adjusted so the breakers closest to the faults open first

Open Transition

Break before make, Open contact with the primary source before closing the secondary source

Closed Transition

Make before break, Closed contact with the secondary source before opening the primary source.

Type of Transition during maintenance bypass

Closed Transition

Type of Transition during a transfer from utility to generator

Open Transition

UPS

Uninterruptible Power Supply - device that allows an electrical system to keep running for at least a short time when incoming power is interrupted until utility or generator provides the power.

Primary Function of the UPS

Uninterruptible Continuous power to the load

Secondary Function of the UPS

Protected power, filters and conditions power preventing damage to the output

UPS Model in Electrical rooms

Schneider Galaxy VX

UPS Model in PPOP and SPOP rooms

Schneider Galaxy VS

Type of UPS

Double Conversion

Output of Electrical Room UPS

1 MW

Output of PPOP and SPOP UPS

50 kW (?)

Major Internal Components of the UPS

Rectifier, Inverter, Batteries, Static Switch, Back Feed Breaker

Rectifier basic function

Converts AC to DC power then filters it through capacitors and trickle charges the batteries.

Inverter Basic Function

Converts DC to AC power via Pulse Width Modulation (PWM) and then filters again through capacitors

Batteries Basic Function

Provides DC power to the inverter should the utility fail

Static Switch Basic Function

Diverts power from the rectifier, inverter, and batteries to the load when there is a fault/failure within the UPS system

Back Feed Breaker Basic Function

Prevents the flow of electricity from going backwards

UPS Modes of Operation

Normal, Static Bypass, Maintenance Bypass, On Battery

UPS MOO - Normal

Power is going through rectifier, trickle charging batteries, then going through inverter to the load.

UPS MOO - Static Bypass

Failure within the internal components of the UPS, power is diverted from those parts

UPS MOO - Maintenance Bypass

Power is diverted from the UPS altogether, UPS system may safely be worked on for maintenance.

UPS MOO - On Battery

Batteries are supplying DC power to the inverter

UPS Sequence of Operation

Under normal conditions, power goes through the rectifier, trickle charges the batteries, through the inverter and to the load.

UPS Alarming Set Points

Over Temperature, Inverter/rectifier failure, fan failure, communication failure, power module failure.

When would maintenance bypass be required?

When performing maintenance on the internal components, diverting power away from the UPS altogether (externally)

When would static bypass be required?

When there is an internal fault or UPS failure, divers power away from the rectifier, battery, and inverter.

Transformer Function

Step-up or Step-down voltages in circuits (AC). DC cannot change voltages.

Delta Transformer Configuration

Three loads connected in a triangle shape

WYE Transformer Configuration

Three loads connected in a Y shape, has a neutral wire which allows for singe-phase AC power.

Step-up Transformers

Voltage is higher on the secondary side, lower current

Step-down Transformer

Voltage is lower on the secondary side, current is higher

Transformer Turn Ratio

The ratio between the number of turns on the primary to secondary sides of the generator. A higher turn ratio means a higher voltage.

PDU

Power Distribution Unit, Converts power via transformer and distributes it to multiple devices.

Output Power Capacities of a PDU

415/240V

PDU Internal Components

Input Breaker, Voltage Transformer, Current Transformer, Sub-feed Output Breakers

PDU Sequence of operations

480 V enter and is converted to dual tap 415/240 V and 208/120V. This is then distributed to the output through the sub-feed output breakers

ATS

Automatic Transfer Switch, device that automatically transfers power from primary source to secondary source if there’s a failure or power outage.

Normal Seeking

Has a preferred power source and will automatically transfer back to this preferred source.

Power Seeking

Does not have a preferred source, staying on the current source unless manually switched back to the primary source.