Review of field acceptance hipot & PD testing of medium voltage underground cables
There are some well-defined guides and standards regarding factory testing of medium voltage shielded cables in laboratories provided by IEEE, IEC, ANSI/ICEA, and CSA. These guides cover AC withstand and PD testing of XLPE and EPR cables and accessories, such as 50/60Hz AC Hipot and PD tests which are routinely conducted on every reel of cable produced at the factory. All terminations, splices, and separable connectors are tested with more or less the same test method using different test levels and timing.
Experience with AC Hipot and Partial Discharge Tests for Commissioning Generating Station Cables and Switchgear
Test equipment is described which is suitable for AC hipot and partial discharge testing of 5 and 15 kV shielded cables of lengths up to about 600 m. The equipment can be used to test 5 and 15 kV metal-clad switchgear. Ontario Hydro's experience at two nuclear generating stations using this AC test equipment is presented. The equipment can be used to assure the integrity of cable systems (less than 600 m long) already in service. The reasons for switching to AC testing of cable systems are outlined. Practical experience shows that the partial-discharge test is very effective in identifying installation problems in cables and switchgear. A number of problems are identified with the AC tests that a DC test would have missed. >
Hedy: A Gradual Language for Programming Education
One of the aspects of programming that learners often struggle with is the syntax of programming languages: remembering the right commands to use and combining those into a working program. Prior research demonstrated that students submit source code with syntax errors in 73% of cases and even the best students do so in 50% of cases. An analysis of 37 million compilations by 250.000 students found that the most common error was a syntax error, which occurred in almost 800.000 compilations. It was also found that Java and Perl are not easier to understand than a programming language with randomly generated keywords, stressing the difficulties that novices face in understanding syntax. This paper presents Hedy: a new way of teaching the syntax of a programming language to novices, inspired by educational methods by which punctuation is taught to children. Hedy starts as a simple programming language without any syntactic elements such as brackets, colons or indentation. The rules slowly and gradually change until the novices are programming in Python. Hedy is evaluated on 9714 programs.