URC Quick-trip™

QUICK-TRIPTM System: 

QUICK-TRIP TM System A Manually Controlled Zone Selective Interlock System for AC-PRO TM Circuit Breaker Trip Units Used on 600V Class Circuit Breakers

Introduction: 

Introduction In recent years more attention is given by codes and standards for the reduction of the arc flash energy hazard to electrical personnel working on energized electrical equipment The NFPA 70E states, “A Flash Hazard Analysis shall be done in order to protect personnel from the possibility of being injured by an arc flash. The analysis shall determine the Flash Protection Boundary and the personal protective equipment that people within the Flash Protection Boundary shall use.”

Flash Hazard Analysis : 

Flash Hazard Analysis A flash hazard analysis consists of 2 parts: Determining the flash hazard boundary Determining the incident energy level the worker would be exposed to The intensity of an arc is based on the following: Amount of available fault current Distance of the electrode gap The clearing time of the protective device The NFPA 70E provides equations as one method of determining the amount of incident energy (heat) a person would receive if an arc flash were to occur

Flash Hazard Analysis: 

Flash Hazard Analysis Excel program using NFPA 70E Equations Download at www.epowerplus.com Example: 36kA available E I at 18”

Introduction: 

Introduction Until now, options for reducing arc flash potential during normal maintenance periods in low voltage substations have been limited. A few of those include: De-energizing the substation during maintenance. Not always a feasible option. Lower the available fault current for the substation. May not be an option at all. Shorten the trip time of the upstream breaker during maintenance periods. Now made fast and easy with QUICK-TRIP TM .

Introduction: 

Introduction One way to reduce the arc flash energy is to reduce the trip time settings of the main (upstream) circuit breaker supplying the electrical equipment that will be worked on while energized. However, selective coordination between circuit breakers will be compromised if the trip time settings are reduced.

System components: 

System components The QUICK-TRIP TM system is activated by means of a padlockable selector switch. When enabled, two additional settings are activated in the AC-PRO trip unit to provide enhanced protection: QT Instantaneous QT Ground Fault These two individually programmable settings are designed to provide faster clearing times in the event of a fault.

System components: 

System components The QUICK-TRIP TM system consists of the following components: A new AC-PRO trip unit with QUICK-TRIP TM capability. All new AC-PRO trip units will now be manufactured with this capability. – A PRO-DISPLAY with QUICKTRIP TM capability, mounting hardware and cable

System components: 

System components A Padlocking selector switch to turn the QUICK-TRIP TM feature ON or OFF. Although all new AC-PRO trip units will have Quick Trip capability, the system can only be activated through the selector switch that connects to the PRO-DISPLAY. – The PRO-DISPLAY connects directly to the AC-PRO through a single modular shielded cable.

Example 1: 

Example 1 Lets say a substation technician needs to rack out a feeder breaker to lock it out for maintenance As the technician is racking out the breaker an arc flash occurs in the switchgear The arcing fault value is 12,000A The 2000A main breaker sees the fault The main breakers short time trip is set at .20s (I 2 t in)

Example 1: 

Example 1 This is the trip curve for a 2000A breaker 12kA will trip the breaker in .556 seconds

Example 1: 

Example 1 A 12 kA fault with a 0.556 second clearing time at 18” E I will be: 10.5 Cal/cm 2 in open air 25.8 Cal/cm 2 in a cubic box

Example 1: 

Example 1 The Personal Protective Equipment (PPE) necessary to perform a task inside of the flash hazard boundary is be determined from the resultant Incident Energy from the flash hazard analysis. The incident energy level determines the Hazard Risk Category (HRC) The arc flash in example 1 had an incident energy level of 25.8 Cal/cm 2 This task would require HRC 4 PPE to perform this task safely Incident Energy Level Hazard Risk Category 0-<4 cal/cm 2 1 4-<8 cal/cm 2 2 8-<25 cal/cm 2 3 25-<40 cal/cm 2 4 >40cal/cm 2 Dangerous

Example 1: 

Example 1 Hazard Risk Category 4 Cotton T-shirt and pants Leather Gloves and Shoes Hard Hat, Liner, Safety Glasses Double layered switching hood and hearing protection Multiple layers of FR clothing or switching suit to equal 40 cal/cm 2

Reducing the hazard: 

Reducing the hazard When electrical personnel must work on energized electrical equipment, they can reduce the arc flash energy hazard by using the QUICK-TRIP TM system. The maintenance personnel would first go to the main breaker feeding the equipment they will be working on and set the selector switch to the “On” position.

Reducing the hazard: 

Reducing the hazard If a fault now occurred, the AC-PRO trip device on the main breaker would act as if it was a trip device on a ZSI system that did not receive a signal from any downstream trip devices. The reduced trip time minimizes the equipment damage and the Arc Flash hazard to the electrical personnel in case a fault occurred. Lets look at the same fault we looked at in example 1 but this time with QUICK-TRIP TM enabled

Example 2: 

Example 2 This is the trip curve for a 2000A breaker with Quick Trip enabled 12kA will trip the breaker in .05 seconds

Example 2: 

Example 2 A 12 kA fault with a 0.05 second clearing time at 18” E I will be: 0.95 Cal/cm 2 in open air 2.32 Cal/cm 2 in a cubic box

Example 2: 

Example 2 The arc flash in example 2 was reduced to an incident energy level of 2.32 Cal/cm 2 This task would require HRC 1 PPE to perform this task safely Incident Energy Level Hazard Risk Category 0-<4 cal/cm 2 1 4-<8 cal/cm 2 2 8-<25 cal/cm 2 3 25-<40 cal/cm 2 4 >40cal/cm 2 Dangerous We have reduced the HRC from 4 to 1 with the flip of a switch!

Typical Protective Clothing: 

Typical Protective Clothing Hazard Risk Category 1 Long sleeve FR Shirt & Pants (Jeans are acceptable) Hard Hat Safety Glasses PPE cal/cm 2 -- ≥ 4.0

Restoring normal protection: 

Restoring normal protection When the work is completed, the QUICK-TRIP TM selector switch is returned to the normal position and the trip device uses its normal trip times. Selective coordination is only lost for the time the electrical personnel are working on the equipment and reduced arc flash hazard is provided during that time.

Summary: 

Summary The best way to protect workers from arc flash hazards is to reduce the hazard The QUICK-TRIP TM system is a simple way to reduce the arc flash hazard for substation operations For more information visit our web site www.utilityrelay.com or call (888)289-2864 For more information about onsite or online NFPA 70E and arc flash training contact Power Plus Engineering at (248) 344-0200 or visit www.epowerplus.com