Data Center Single Line Diagrams, Drafting Principles, and Instrumentation Control Loops (copy)

Single-Line Diagram (SLD)

A diagram that represents the power distribution topology of facilities such as data centers.

Main Breaker (MB)

The primary switch that controls the electrical supply for a facility.

Utility Main Breaker (UMB)

A breaker that protects the incoming utility power supply.

Standby Generator

An on-site backup generator that supplies secondary power controlled by a generator breaker.

Power Distribution Cabinet (PDC)

A cabinet that receives power from feeder breakers and distributes it to individual server racks.

Cascading Trip Sequence

A sequence of actions where protective breakers open in response to electrical faults, beginning with the most localized breaker.

Potential Transformer (PT)

A transformer that steps down system operating voltage for safe measurement.

Current Transformer (CT)

A transformer that samples line current and sends reduced output to monitoring relays.

Static UPS System

A power supply system that includes a rectifier, battery bank, inverter, and static transfer switch.

ANSI Device 51

An inverse-time AC overcurrent relay that trips faster with higher overcurrent levels.

Cascaded Control Loop

A control loop design where one controller influences another, allowing for modular design and specialized function.

Set Point (SP)

The desired target value for a controlled variable in a control loop.

Process Variable (PV)

The actual value of a measured parameter in a control loop.

Signal Line Convention: Solid Line

Indicates process piping containing the main process fluid.

Signal Line Convention: Dashed Line

Indicates electrical transmission signals.

ISA Tag Lettering: A

Designates an Analysis element in instrument tagging.

Dimension Line

Lines terminating in arrowheads indicating measurement extent in technical drawings.

Hidden Lines

Dashed lines that represent hidden internal edges or surfaces in engineering drawings.

Leader Line

A line that connects a note or dimension to a specific feature of an object.

Hydraulic Valve

A valve actuated by hydraulic pressure and using hydraulic signal lines.

Motor-Operated Valve (MOV)

A valve actuated by an electric motor, often controlled via electrical signals.

Decentralized Backup Power

Emergency power provided individually to racks to prevent total facility power loss.

Protective Breakers

Devices designed to isolate faults at the closest point to protect electrical systems.

Breaker Isolation

The method of protecting downstream equipment by isolating faults at the nearest breaker.

Arc Dimensioning

Defined by their radius (R), allowing for identification of curvatures in mechanical drawings.

Cascading Trip Action

A method of fault isolation where the action cascades upstream if the fault cannot be cleared.

Visible (Object) Lines

Thick, solid lines that define visible edges of an object in engineering drawings.

Pneumatic Control Valve

A valve that is actuated by compressed air and controlled through pneumatic signal lines.

Schematic Cross-Referencing

The matching of a contactor to its controlling coil through alphanumeric identifiers.

Final Control Element

Mechanical assemblies like valves that adjust flow rates or pressure in a control loop.

Maintenance Bypass Synchronization

The requirement for synchronized AC sources during maintenance to prevent electrical stress.

Differential Protective Relay (Device 87)

A relay that detects differences in currents to provide fault protection.

Under/Over Frequency Relay (Device 81)

A relay that trips if the facility frequency falls outside normal limits.

Fault Isolation

The principle of identifying and shutting down faults to maintain operational integrity.

Uninterruptible Power Supply (UPS)

A backup power supply system that provides emergency power when the main source fails.