The National Grid Network

         The National Grid Network is an important system that ensure the electrical power is supplied continuously. After the generation of electricity at the power station, electricity is transferred via a number of substations and transformers before the electricity reaches the customer.

Table 10.1 shows current and potential difference before and after substation A in a transmission of electricity.

  Rangkaian Grid Nasional merupakan satu system yang penting untuk memastikan bekalan kuasa elektrik adalah berterusan. Selepas tenaga elektrik dijanakan di stesen janakuasa, tenaga elektrik itu akan dipindah melalui beberapa substation yang mengandungi transformer sebelumsampai ke penggunanya.

Jadual 10.1 menunjukkan arus dan beza keupayaan tenaga elektrik sebelum dan selepas melalui suatu substation A semasa penghantaran tenaga elektrik.

Physical quantity Kuantiti Fizik	Transmission of electricity Penghantaran tenaga elektrik
	Before substation A Sebelum melalui substesen A	After substation A Selepas melalui substesen A
Current Arus	80 A	15 A
Potential Difference Beza keupayaan	25 kV	132 kV

Table 10.1

Jadual 10.1

Table 10.2 shows current and potential difference before and after passing through substation B during reception of electricity by customers.

Jadual 10.2 menunjukkan arus dan beza keupayaan tenaga elektrik sebelum dan selepas melalui suatu substesen B semasa penerimaan tenaga elektrik oleh pengguna.

Physical quantity Kuantiti Fizik	Transmission of electricity Penerimaan tenaga elektrik
	Before substation B Sebelum melalui substesen B	After substation B Selepas melalui substesen B
Current Arus	15 A	60 A
Potential Difference Beza keupayaan	132 kV	33 kV

Table 10.2

Jadual 10.2

(i)	What is meant by potential difference? Apakah yang dimaksudkan dengan beza keupayaan?  [1 mark] [ 1 markah]

(b)

Using only information in table 10.1 and 10.2, compare characteristics of electrical power transmitted and received by customers. States the relationship between current and potential difference during transmission and reception of electrical power. Menggunakan hanya maklumat dalam jadual 10.1 dan 10.2, bandingkan ciri-ciri kuasa elektrik yang dihantar dan diterima oleh pengguna. Seterusnya nyatakan hubungan antara arus dengan beza keupayaan semasa penghantaran dan penerimaan tenaga elektrik.  [5 marks] [ 5 markah] Generation of electrical power involves the use of renewable resources and unrenewable resources. With the use of suitable examples, compare the two types of resources. Penjanaan kuasa elektrik melibatkan penggunaan sumber tenaga yang boleh diperbaharui dan yang tidak boleh diperbaharui. Dengan menggunakan contoh-contoh yang sesuai, bandingkan kedua-dua jenis sumber itu.  [4 marks]/[4 markah]                                           (c) During transmission and reception of electrical power, pylons such as shown by diagram 10.1 play an important role. Based on diagram 10.1, your knowledge about transmission of electrical power and other related physics concept, explain: (i)the characteristics of materials used to build the pylons. (ii)the design of the pylons. (iii)the characteristics of the cable used in the electrical power transmission. Semasa penghantaran dan penerimaan tenaga electrik, tiang-tiang seperti pada rajah 10.1, memainkan peranan yang sangat penting. Berdasarkan rajah 10.1, pengetahuan anda tentang penghantaran kuasa elektrik dan konsep fizik lain yang berkaitan, terangkan: (i)ciri-ciri bahan yang digunakan untuk membina tiang-tiang tersebut. (ii)Rekabentuk tiang-tiang. (iii)ciri-ciri kabel yang digunakan untuk penghantaran tenaga elektrik. ANSWER Work done to transfer 1 C charges from one point to another Electrical power is generated at high current and low voltage Before transmission, current passes through step up transformer During transmission, electrical power is at low current and high voltage to reduce power loss  At reception point, current passes through step down transformer At reception, electrical power is at low voltage and high current                                                                                                      Nonrenewable resources  natural gas, petroleum      will be depleted                                                         pollute the  environment  Renewable resources  hidro, solar & wind                                         Will not be depleted           does not pollute environment   Characteristic     Explaination Material:  steel alloy Strong, will not breake easily   U shape steel alloy   Not too heavy   Trust and support join   Can support bigger weight   Large diameter cable      Less resistance   made from small diameter and laminated wire Reduce eddy current     Cable made from low density material   Cable is not heavy