Unit 1: Tariff & Power Factor Correction

Understand tariff and power factor correction Understand the tariffs for consumers Understand the methods to improve power

factor

Understand tariff & power factor correction The use of tariff & power factor

Tariff : to determine payment for electricity used by consumers

Power factor : determine the value of power and efficiency

Definition of tariff & power factor Tariff : electricity payment scale charged by supplier

(TNB) Power factor :

Ratio between real power (watt) and apparent power (VA) Cosine angle that separate watt and volt-ampere

Understand tariff & power factor correction

Perbelanjaan bagi mengeluarkan tenaga elektrik :

Kos tetap Perbelanjaan asas yg perlu dikeluarkan oleh pembekal Pembinaan penjana, penghantaran dan pengagihan, gaji

pekerja, insurans dll.

Kos berubah Perbelanjaan yg kadarnya bergantung kpd jumlah tenaga yg

dikeluarkan Kos-kos tambahan unit bahan api dan air, penggantian alat-

alat loji dll

Understand tariffs for consumers

Three types of common tariffs

1) Flat rate (Kadar sama rata/sekata) Devide rate into 2 parts – lamps & power Need 2 units of kilowatt hour meter More usage, more you pay

Understand tariffs for consumers

Three types of common tariffs1) Flat rate (Kadar sama rata/sekata)

How this tariff is used Only for small industries

CalculationLamps = 100 units x RM0.20

= RM 20.00Power = 200 units x RM0.25

= RM 50.00Total = RM 70.00

Tariffs for consumers

Three types of common tariffs

2) Two parts rate (kadar dua bahagian) : Directly devided into 2 parts Use only 1 kilowatt hour meter 1st part : maximum demand payment (base on

consumer’s need) 2nd part : used power units in a month

Tariffs for consumers Three types of common tariffs

2) Two parts rate (kadar dua bahagian) : How this tariff is used

For big factories/industries CalculationMax. demand = 4kW x RM12.00

= RM 48.00Units used = 200 units x RM0.07

= RM 14.00Total = RM 62.00

Tariffs for consumers

Three types of common tariffs

3) Block rate Devide into 3 payment scale:

1st scale: if more than some units (eg. 100 units) 2nd scale: balance of 1st scale, if more than some

units (eg. 50 units) 3rd scale: balance of 2nd scale, if more

Use only 1 units of kilowatt hour meter

Tariffs for consumers

Three types of common tariffs

3) Block rate How this tariff is used

Housing area

Calculation1st 100 units = 100 x RM0.20 = RM 25.00

2nd 50 units = 50 x RM0.20 = RM 10.00

Balance 150 units = 100 x RM0.20 = RM 34.50

Total = RM 69.50

Methods to improve power factor Various methods to improve power factor

Phase (Pemaju fasa) Mesin khas yg disambungkan secara selari dgn motor/alat yg boleh

merendahkan faktor kuasa Dihidupkan/dimatikan bersama-sama dgn motor/alat

Synchronous motor (Motor segerak) Saiz besar Dipasang selari dgn palang bas bekalan motor boleh berfungsi seperti biasa semasa pembaikan faktor dibuat

Capacitor (Pemuat) Komponen paling murah dan mudah digunakan, tidak memerlukan

kawasan yg besar, kenaikan suhunya rendah dan kehilangan kuasanya boleh diabaikan

Dipasangkan selari dgn peralatan

Methods to improve power factor Disadvantages for low power factor

Perbelanjaan utk membekalkan tenaga elektrik adalah lebih besar kerana voltan perlu dinaikkan utk mendapat kuasa yg sama dgn tenaga elektrik yg dikeluarkan pada faktor kuasa yg tinggi. Ini melibatkan peralatan seperti penjana, pengubah, sius peralatan dll.

Jika voltan sukar dinaikkan, maka arus perlu dinaikkan bagi memperolehi kuasa yg serupa dgn kuasa ketika faktor kuasa tinggi. Saiz kabel dan kadar arus alat perlu ditukar dan mengakibatkan perbelanjaan yg lebih. Kehilangan kuprum (I2R) dan susut voltan pada kabel (IR) akan bertambah.

Seterusnya kecekapan alat akan berkurang.

Methods to improve power factor How to calculate power factor correction

Seorang pengguna kuasa menggunakan permintaan maksima sebanyak 250kW utk tempoh setahun. Tarif yg ditawarkan ialah RM140 setiap kW permintaan maksima setahun, tambah RM0.20 bagi setiap unit. Unit yg digunakan sebanyak 350000 pada faktor kuasa satu. Kira kos utk tempoh setahun dan harga purata per unit.

Penyelesaian:Kos setahun = RM (140x250) + (350000x0.20)

= RM (35000) + (70000) = RM 105000

Harga purata per unit = 105000 / 350000 = RM 0.30

Methods to improve power factor How to calculate power factor correction

Pengguna yg sama juga mempunyai faktor kuasa 0.6 menyusul. Tarif yg dikenakan ialah RM 140.00 bagi setiap kVA permintaan maksima dalam setahun, tambah RM0.20 bagi setiap unit. Kira kos utk tempoh setahun dan harga purata per unit.

Penyelesaian:kVA permintaan maksima = kW / faktor kuasa

= 250 / 0.6 = 416.66 kVA

Kos setahun = RM (140x416.66) + (350000x0.20) = RM (58332.40 + 70000) = RM 128332.40

Harga purata per unit = 128332.40 / 350000 = RM 0.36