问题 单项选择题

某220kV配电装置内的接地网,是以水平接地极为主,垂直接地极为辅,且边缘闭合的复合接地网,已知接地网的总面积为7600m2,测得平均土壤电阻率为68Ω.m,系统最大运行方式下的单相接地短路电流为25kA,接地短路电流持续时间2s。据以上条件回答下列问题。

假设220kV变压器中性点直接接地运行,流经主变压器中性点的最大接地短路电流值为1kA,厂内短路时避雷线的工频分流系数为0.5,厂外短路时避雷线的工频分流系数为0.1,计算220kV配电装置保护接地的接地电阻应为下列何值?()

A.5Ω

B.0.5Ω

C.0.39Ω

D.0.167Ω

答案

参考答案:D

单项选择题
阅读理解

阅读理解。

                                                                           PENRICE 

                                                                COMMUNITY COLLEGE

                                                                Cornwall Country Council

                                                 WE NEED TWO ASSISTANT HEADTEACHERS

                                                                     From January 2006 

                                                                L13-17(£44 703-£49 314)

      Penrice Community College is a highly regarded and successful 11-16 specialist languages college.

Following the recent appointment of a new Headteacher we're restructuring(重组)the leadership team

to create new roles.

     One post will be leading teaching teams with responsibility for curriculum and timetabling.

     The other post will be leading student based teams with responsibility for student learning outcomes

and the removal of barriers to student success such as poor attendance or disaffection.

     Penrice Community College is:

     ● A school with 1350 wonderful students

     ● High achieving with results well above average

     ● Mentioned twice in HMCI's outstanding schools list

     ● A british Council International School

     ● Situated in a beautiful part of mid Cornwall All enquires for information and application packs to

Daniellle Eyres on 01726 72613 or on secretary @ penricecornwall. Sch. Uk Closing date for applications

is Tuesday October 4th at noon. Interviews will be held on Monday 17th and Tuesday 18th October 2005.

1. The purpose of the above passage is to _____.

A. introduce the advantage of a school

B. report the appointment of a new headteacher

C. call on more students to go to school

D. advertise for new assistants of headteachers

2. The two new posts are required to do all the following EXCEPT ______.

A. stopping students missing classes

B. getting students interested in learning

C. leading student based teams

D. arranging new curriculum

3. HMCI is probably the name of _____.

A. an educational organization

B. a school leader

C. a political party

D. a news reporter

4. How many ways are mentioned in which you can get in touch with the school?

A. Two

B. Three

C. Four

D. Five