IEEE 1584 Working Group Moves Forward with New Modeling and Standard Revisions
On Sunday 1/30/12, members of the IEEE 1584 Working Group met in Daytona Beach, FL to discuss the latest IEEE/NFPA Collaboration Testing report and to discuss changes to the IEEE 1584 Standard. The meeting was attended by approximately 48 engineers and technicians from across the United States and Canada.
The IEEE/NFPA Collaboration Study is an attempt to improve the energy and arc flash boundary equations currently shown in the guide. A significant increase in the number of tests is being undertaken to study the effects of (1) Heat and Thermal effects, (2) Blast Pressure, (3) Sound, and (4) Light hazards. These tests are being done at 600, 2,400, 4,160, and 13,800 Volt equipment. Some tests at 208 Volts have been done in an attempt to determine the minimum size that will sustain an arc flash on the secondary terminals. (See the discussion in previous blog entries and below)
One of the more interesting phenomenons is the extremely high light level that occurs for an arc flash. Tests have shown that some of the arc flash tests had light levels of 120 times that of looking at the sun. This high level surprised the testing group. Future NFPA 70E revisions will most likely add arc flash eye protection similar to welding flash eye protection.
The testing group plans to deliver a draft model (equations) by April 2012 to the IEEE 1584 working group members. It will be our job to try out the model and see how they compare to the past 1584 equations and Lee equations.
After April, the testing group will proceed with DC arc flash testing with the goal of developing a model for DC arc flash energies and boundaries.
The current standard published the equations and provided the user with an Excel Spreadsheet with the equations imbedded. It allowed the user to calculate the energy levels and arc flash boundaries. The IEEE/NFPA Collaboration group feels that equations in the current standard have been copied, used in other computer programs and at times, misapplied.
The new standard will use a “Black Box” method of calculation. The new standard will include an executable program that will allow the user to input the appropriate data and the arc flash energy and boundary will be displayed. Neither equations nor spreadsheet to show what the equations are will be provided. Software companies such as SKM, ETAP, EasyPower, and others will license the “Black Box” function from IEEE. The software companies will imbed this black box program into their software.
The IEEE 1584 Committee has a very ambitious schedule. The current schedule will have the Standard revised, approved, and voted on by the end of 2012.
While the testing group continues their efforts, the 1584 committee members continued to revise the current text.
One of the most controversial items in the current Standard 1584® IEEE Guide for Performing Arc-Flash Hazard Calculations is the exemption for systems less than 240 volts and fed by transformers rated 125 kVA or less. Section 4.2 page 6 states, “Equipment below 240 V need not be considered unless it involves at least one 125 kVA or larger low impedance transformer in its immediate power supply.”
There are two problems with this statement. The first is that IEEE 1584 Standard is for three phase systems only and it is not to be used for single phase systems. A 125 kVA transformer is a standard single phase transformer size and not a standard three phase transformer (the closest standard three phase size is 112.5 kVA)
The second problem is the assumption that there is no serious arc flash hazard for these systems. Testing last spring by the IEEE/NFPA Collaboration group found that some 208 Volt transformer secondaries can sustain an arc flash. Most of the IEEE 1584 working group members feel that 125 kVA is too high but the group could not come to a consensus as to what the lower transformer size should be.
A motion was made and approved to form a subcommittee to continue the discussion and investigation of this very important cut off transformer size.