What is PD IEC 61956 - Water treeing in insulating materials about?       
PD IEC 61956 guideline provides methods of test for the evaluation of water treeing in polyethylene (PE) and crosslinked polyethylene (XLPE) compounds, as a means to assess their relative performance under alternating (a.c.) electric stress, in the presence of water. 
PD IEC 61956 provides you with two methods, method I cover the evaluation of insulating materials alone, and method II covers the evaluation of insulating sandwiches consisting of insulating material in intimate contact with semiconducting screens. 
Who is PD IEC 61956 - Water treeing in insulating materials for?   
PD IEC 61956 on water treeing in insulating materials is useful for:   
- Cable manufacturers
- Manufacturers of insulators
- Quality control personnel
- Manufacturers of electrical and electronic appliances
- Electrical engineers    
Why should you use PD IEC 61956 - Water treeing in insulating materials?    
Water treeing is one of the major causes of premature ageing and failure of extruded medium voltage cables which do not have water-impervious barriers. Besides technological efforts, it has been a challenge to overcome such failures by improving insulating compounds, based on chemically crosslinked low-density polyethylene (XLPE). 
Consequently, a need for suitable material test methods has arisen; primarily for a meaningful screening test to evaluate the water tree propensity of such materials, and thus reduce the need of cable testing to compare and preselect materials.  
Method I in PD IEC 61956 subjects easily producible plaque-type test specimens to a divergent (variant A) or a uniform (variant B) a.c. electric stress while immersed in a wet environment. A newly developed test cell allows evaluating either vented water trees (vt) in front of indentations (A) or bows tie water trees (btt) at imperfections (B) within the test specimen, or both types simultaneously.
Method II in PD IEC 61956 ages cup-shaped test specimens, made of insulating material sandwiched between two layers of semiconducting screen material, under uniform a.c. electric stress while exposed to a wet environment. In addition to microscopic inspection of water trees (vt and btt), this method enables an evaluation by electrical breakdown tests. 
PD IEC 61956 helps you lower the premature ageing and failure of extruded medium voltage cables.    
