Guide to calculating arc flash from methods and steps
Calculating arc flash is very important for you
to get the best arc flash protection relay. This article will provide an
in-depth introduction to four methods for calculating arc flash in the power
industry, including arc flash hazard calculation, arc short circuit
calculation, arc flash accident energy calculation, arc flash boundary
calculation, and steps for calculating arc flash.
1. 4 Methods for calculating arc flash
1.1 Arc flash hazard calculation
Arc flash hazard calculations are a method based on the IEEE 1584 standard, which guides performing arc flash hazard calculations. The method involves bolt fault current, review of arc flash formulas, presentation of arc flash formulas, and formatted arc flash formulas. Through this calculation method, potential arc flash hazards can be determined so that appropriate protective measures can be taken.
IEEE 1584 standard formula:
Iarc=K⋅Ibfa⋅db⋅tc⋅AF
Here, Iarc is the arc current, Ibf is the bolted fault current, d is the working distance, t is the arc duration, and AF is the adjustment factor. The constants K,a,b,c are specific values defined by the IEEE 1584 standard.
Calculation Example:
Let’s assume a bolted fault current Ibf=10,000 Amperes, working distance d=300 millimeters, arc duration t=0.1 seconds, and adjustment factor AF=1.
By inserting these values into the formula, we can calculate the arc current Iarc
Iarc=K⋅(10,000)a⋅(300)b⋅(0.1)c⋅1
Note that the values for constants K,a,b,c need to be obtained from the IEEE 1584 standard based on specific power system and equipment parameters.
1.2 Arc short circuit calculation
Arc short circuit calculations are used to determine the arc characteristics when a short circuit occurs in a power system. This includes analysis of various fault types in the system and calculation of corresponding arc parameters.
Arc parameter calculation:
Arc short circuit calculations involve the following key arc parameters:
Arc Current Calculation:
In arc fault current calculation, determining the arc current (Iarc) often involves system voltage, impedance, and reactance parameters. Here is a simplified example:
Iarc=ZtotalUsystem
Here, Usystem is the system voltage, and Ztotal is the total impedance.
1.3 Arc flash accident energy calculation
Arc flash accident energy calculations are designed to evaluate the energy release of arc flash accidents. This involves the measurement and evaluation of arc energy.
Arc energy calculation:
Earc=Parc⋅t
Earc is the energy of the arc incident (joules).
Parc is the power of the arc (watts)
t is the arc duration in seconds.
If you know the arc voltage, current, and duration, we can calculate the energy of an arc incident.
1.4 Arc flash boundary calculation
Arc flash boundary calculations are performed to determine the boundaries of potential arc hazards in power systems to ensure that personnel within the hazardous area take appropriate protective measures.
Safety boundary calculation:
System parameters: including current, voltage, etc.
Arc characteristics: including arc current, voltage, energy, etc.
Human Protection: Determine the safe distance required to protect people.
Calculation of safety margins often involves complex electromagnetic and thermal parameters, but in general, variations of the following formulas can be used.
Safe Distance=f(Uarc,Iarc,Earc,Protection Factors)
Here, Uarc,Iarc,Earc represent arc voltage, current, and energy, while Protection Factors combine various factors related to personnel protection. The specific formula and parameters for safe distance depend on the actual circumstances.
Please note that these calculation examples serve as conceptual demonstrations, and actual applications require detailed calculations based on specific power system parameters, equipment characteristics, and standards.
2. Detailed steps for calculating arc flash
2.1 Collect system data:
The first step in arc flash calculations is to collect critical power system data. These data include:
System topology: Describes the physical layout of a power system, including the connections and locations of generators, transformers, switchgear, etc.
Component parameters: Including parameters of each electrical device, such as resistance, inductance, capacitance, etc., as well as system current and voltage ratings.
System working conditions: Record the working conditions of the system during normal operation, such as current, voltage, frequency, etc.
The accuracy of this data is critical to subsequent calculations, thus ensuring that the information collected is up to date and accurate.
2.2 Select calculation method:
Select an appropriate arc flash calculation method based on the system data collected. Generally, the following calculation methods can be selected according to the characteristics of the power system:
Arc flash hazard calculation: Based on the IEEE 1584 standard, considering parameters such as bolt fault current, working distance, arc duration, etc.
Arc Short Circuit Calculation: Used to determine arc characteristics, taking into account the various types of faults that may occur in the system.
Arc Flash Incident Energy Calculation: Evaluate the energy release of an arc incident, considering arc power and duration.
Arc Flash Boundary Calculation: Used to determine the boundaries of potential arc hazards to ensure that personnel within the hazardous area take appropriate protective measures.
These calculation methods are considered together to obtain a complete understanding of the potential arc hazard of the system.
2.3 Perform calculations:
Perform arc flash calculations using the selected calculation method. Based on the specific calculation formulas and parameters, results such as arc flash hazard level, accident energy level, and boundary location are obtained. These calculations often require the use of professional power system analysis software for precise calculations.
2.4 Assess risks:
Based on the calculation results, evaluate potential arc flash risks. Consider the hazards that arc accidents may cause to personnel and equipment and determine whether there are safety hazards. This step is the basis for ensuring that appropriate measures are taken.
2.5 Develop safety measures:
Based on the risk assessment results, formulate and implement appropriate security measures. This may include:
Personnel training: Employees should understand the dangers of arc flash and learn the correct response methods.
Use of protective equipment: Provide appropriate protective equipment, such as fire-resistant clothing, masks, etc., to reduce damage from arc accidents.
Safe operating procedures: Develop clear operating procedures to ensure that personnel follow safe operating standards in the power system.
2.6 Periodic review:
Because power systems may change, it is critical to review arc flash calculations regularly. Ensure that changes in system parameters, equipment configurations, etc. are taken into account and that risk assessments and corresponding security measures are updated in a timely manner.
Through the above steps, the power industry can conduct arc flash calculations comprehensively and scientifically to ensure the safety and reliability of the working environment.
