Table of Contents
A proper and adequate creepage distance protects against tracking, a process that produces a partially conducting path of localized deterioration on the surface of an insulating material as a result of the electric discharges on or close to an insulation surface.
Why is creepage distance important?
The isolation required between parts with different operating voltages, to prevent against unacceptable risk, is the primary reason for the importance of creepage and clearance distances. It [creepage] is the shortest distance between two conductive parts, measured through air.
What is the meaning of creepage distance?
Creepage distance means the shortest distance along the surface of a solid insulating material between two conductive parts. The values of table “Creepage distances to avoid failure due to tracking” are based upon existing data and are suitable for the majority of applications.
How can creepage distance be improved?
Thinking back to the mountaintop metaphor, one way to increase creepage is to make a valley between the peaks. You can cut grooves or troughs into the PCB substrate to increase creepage. You can also sometimes cut slots all the way through the insulator to increase the distance.
How do you measure creepage distance?
How to Determine Creepage Distance for Connectors Creepage Distance/Air Gap: The Path of Least Resistance. Check the Pins on the Connector Face. Check the Backside of the Connector: Check Female Contacts as well: Check For Hidden Creepage Paths Inside the Connector. Check for Hidden Creepage Paths Outside the Connector.
What causes creepage?
This can include an accumulation of conductive contaminants that can become conductive with moisture (i.e. dust). This also includes periodic overvoltage events on the mains voltage. These events can be caused by a number of normal situations including weather and switching induced overvoltages.
What is tracking in electrical?
Tracking is defined as a process that produces localised irreversible deterioration on the surface of an insulator, resulting in the loss of the insulating function by the formation of a conductive path on the surface of the insulator.
What are the types of insulators?
A look at some types of insulators and the conditions under which they are deployed. Pin-type insulators. Line post insulators. Suspension insulators. Strain insulators. Shackle insulators. Post insulators. Cap and pin insulators. Stay insulators.
What is flashover distance?
Strike distance is simply the shortest distance between the end fittings of the insulator in the surrounding medium. It is also sometimes referred to as the dry arc distance, flashover distance, or tight string distance. The higher the operating voltage, the greater strike distance you will need.
What is the creepage distance of insulator?
The distance measure of along the surface of the solid insulating material is called creepage distance. The creepage distance is depending upon the weather condition. Minimum creepage distance are 16-25 mm/kV.What is Creepage and Clearance Distance of Insulator? S No. Degree of Pollution Recommended Creepage Distance for Insulators 4 Heavily polluted areas 25 mm/kV +.
What is current creepage?
Creepage is defined as the shortest distance between two conductive paths measured along the surface of a solid insulation. The shortest path is typically found around the end of the package body between conductive pins or leads.
What is dry arcing distance?
Dry arcing distance is the shortest distance outside the insulator along the air not along the insulator body and between those parts which normally have the operating voltage between them. Arcing distance is also called as flash over distance.
What is voltage creep?
Creepage or creep distance is pretty simple. It represents the shortest distance along the surface of the insulator between the conductive ends of the insulator. In a typical insulator application, one end would be at an elevated voltage level and the other end would be at a lower voltage or grounded.
How does PCB measure creepage distance?
Use V-groove, notch, and slot techniques for creepage issues in a PCB. Default situation of a flat insulating surface: In this method, the creepage is measured along the PCB surface between two conductors. You can increase the creepage distance by increasing the distances between the traces.
What is creepage in high voltage?
CREEPAGE: The shortest path between two conductive parts, or between a conductive part and the bounding surface of the equipment, measured along the surface of the insulation (Figure 2). One additional term that is related to these definitions in a high voltage design is “bounding surface.”.
What is PCB voltage?
Although power supply circuit boards are classified according to their output voltage and power. There is no universally accepted definition for high voltage; however, the generally accepted level for industrial circuitry is ≥ 100V (AC or DC).
What is tracking in High Voltage?
The High Voltage Tracking Resistance (HVTR) test method is used to assess the susceptibility to tracking of insulating materials that are exposed to high voltages outdoors. Their electrical insulation properties can deteriorate to such an extent as a result that tracking paths are formed on the insulator surface.
What is treeing and tracking?
The spreading of spark channels during tracking, in the form of the branches of a tree is called treeing. Tracking is the formation of a continuous conducting paths across the surface of the insulation mainly due to surface erosion under voltage application.
What is insulation tracking?
Surface Tracking is the propagation of an electrically conductive path along the surface of an electrical insulator due to the breakdown of the insulation material. Tracking develops from surface discharge activity associated with the flow of leakage current, especially under wet or contaminated conditions.
What are 4 types of insulators?
Types of Insulators Pin Insulator. Suspension Insulator. Strain Insulator. Shackle Insulator. Post-Insulator. Stay Insulator. Disc Insulator.
What are 5 insulators?
Insulators: glass. rubber. oil. asphalt. fiberglass. porcelain. ceramic. quartz.
What are 4 examples of insulators?
Examples of insulators include plastics, Styrofoam, paper, rubber, glass and dry air.
What causes a flashover?
Flashover is a thermally-driven event during which every combustible surface exposed to thermal radiation in a compartment or enclosed space rapidly and simultaneously ignites. Flashover normally occurs when the upper portion of the compartment reaches a temperature of approximately 1,100 °F for ordinary combustibles.
What is flashover test?
Impulse frequency flashover test An impulse voltage generator which generates a very high voltage at a frequency of several hundred kilohertz is connected to the insulator. This voltage is applied to the insulator and spark-over voltage is noted.
What is the distance between the EHV lines and earth?
For reasons of limiting overvoltage, single-segment EHV transmission lines should not exceed 500 km and EHV transmission lines with switching stations in the middle should not exceed 2×350 km.
