Consider the following statements regarding Line Commutated Converters (LCC):
1. They require a strong AC system for commutation.
2. They can operate without reactive power support.
3. Commutation failure can occur due to AC faults.
Which options stated above is/are correct?
Answer & step-by-step solution
Line-commutated HVDC uses thyristors and depends on the AC system voltage for commutation, so adequate short-circuit strength and reactive-power support are important. AC voltage disturbances can produce commutation failure, particularly at the inverter. Key relation: LCC reactive demand is a significant fraction of transmitted power and is compensated locally.
Exam focus: Strong AC system and commutation margin matter for LCC. Common trap: LCC cannot normally operate a passive AC network without a voltage source.
Statement-wise Verification
- Statement 1 - Correct.
They require a strong AC system for commutation.
Strong AC system and commutation margin matter for LCC. - Statement 2 - Incorrect.
They can operate without reactive power support.
LCC converters consume reactive power and normally require compensation/support - Statement 3 - Correct.
Commutation failure can occur due to AC faults.
AC voltage disturbances can produce commutation failure, particularly at the inverter.
Core Concept
Line-commutated HVDC uses thyristors and depends on the AC system voltage for commutation, so adequate short-circuit strength and reactive-power support are important. AC voltage disturbances can produce commutation failure, particularly at the inverter.
Formula / Key Relationship
LCC reactive demand is a significant fraction of transmitted power and is compensated locally.
Why the Other Options Are Wrong
Option B is incorrect because it includes incorrect statement(s) 2 and omits correct statement(s) 1, 3. Option C is incorrect because it omits correct statement(s) 3. Option D is incorrect because it includes incorrect statement(s) 2.
Exam Shortcut / Approach
Strong AC system and commutation margin matter for LCC.
Common Mistake
LCC cannot normally operate a passive AC network without a voltage source.
Quick Revision
Commutation and AC System Strength is linked with LCC-HVDC, HVDC Transmission and Power Systems. Strong AC system and commutation margin matter for LCC.
लाइन कम्यूटेटेड कन्वर्टर (LCC) के संबंध में निम्नलिखित कथनों पर विचार कीजिए:
1. कम्यूटेशन के लिए इन्हें मज़बूत AC प्रणाली की आवश्यकता होती है।
2. ये प्रतिक्रियाशील शक्ति (reactive power) समर्थन के बिना कार्य कर सकते हैं।
3. AC फॉल्ट के कारण कम्यूटेशन विफलता हो सकती है।
ऊपर बताए गए कौन-से विकल्प सही हैं?
उत्तर और चरणबद्ध हल
A — केवल 1 और 3। LCC HVDC थाइरिस्टर उपयोग करता है और कम्यूटेशन के लिए AC प्रणाली वोल्टेज पर निर्भर है, इसलिए मज़बूत AC प्रणाली चाहिए। यह बड़ी मात्रा में प्रतिक्रियाशील शक्ति खपत करता है (स्थानीय क्षतिपूर्ति आवश्यक), और AC वोल्टेज गड़बड़ी से कम्यूटेशन विफलता होती है।
विस्तृत हल (मूल भाषा में)
Statement-wise Verification
- Statement 1 - Correct.
They require a strong AC system for commutation.
Strong AC system and commutation margin matter for LCC. - Statement 2 - Incorrect.
They can operate without reactive power support.
LCC converters consume reactive power and normally require compensation/support - Statement 3 - Correct.
Commutation failure can occur due to AC faults.
AC voltage disturbances can produce commutation failure, particularly at the inverter.
Core Concept
Line-commutated HVDC uses thyristors and depends on the AC system voltage for commutation, so adequate short-circuit strength and reactive-power support are important. AC voltage disturbances can produce commutation failure, particularly at the inverter.
Formula / Key Relationship
LCC reactive demand is a significant fraction of transmitted power and is compensated locally.
Why the Other Options Are Wrong
Option B is incorrect because it includes incorrect statement(s) 2 and omits correct statement(s) 1, 3. Option C is incorrect because it omits correct statement(s) 3. Option D is incorrect because it includes incorrect statement(s) 2.
Exam Shortcut / Approach
Strong AC system and commutation margin matter for LCC.
Common Mistake
LCC cannot normally operate a passive AC network without a voltage source.
Quick Revision
Commutation and AC System Strength is linked with LCC-HVDC, HVDC Transmission and Power Systems. Strong AC system and commutation margin matter for LCC.
લાઇન કમ્યુટેટેડ કન્વર્ટર (LCC) અંગે નીચેનાં વિધાનો ધ્યાનમાં લો:
1. કમ્યુટેશન માટે તેમને મજબૂત AC પ્રણાલીની જરૂર પડે છે.
2. તે પ્રતિક્રિયાશીલ પાવર (reactive power) સહાય વિના કાર્ય કરી શકે છે.
3. AC ફોલ્ટને કારણે કમ્યુટેશન નિષ્ફળતા થઈ શકે છે.
ઉપર જણાવેલા કયા વિકલ્પો સાચા છે?
જવાબ અને પગલાવાર ઉકેલ
A — ફક્ત 1 અને 3. LCC HVDC થાઇરિસ્ટર વાપરે છે અને કમ્યુટેશન માટે AC પ્રણાલીના વોલ્ટેજ પર આધાર રાખે છે, તેથી મજબૂત AC પ્રણાલી જોઈએ. તે મોટા પ્રમાણમાં પ્રતિક્રિયાશીલ પાવર વાપરે છે (સ્થાનિક વળતર જરૂરી), અને AC વોલ્ટેજ ખલેલથી કમ્યુટેશન નિષ્ફળતા થાય છે.
વિગતવાર ઉકેલ (મૂળ ભાષામાં)
Statement-wise Verification
- Statement 1 - Correct.
They require a strong AC system for commutation.
Strong AC system and commutation margin matter for LCC. - Statement 2 - Incorrect.
They can operate without reactive power support.
LCC converters consume reactive power and normally require compensation/support - Statement 3 - Correct.
Commutation failure can occur due to AC faults.
AC voltage disturbances can produce commutation failure, particularly at the inverter.
Core Concept
Line-commutated HVDC uses thyristors and depends on the AC system voltage for commutation, so adequate short-circuit strength and reactive-power support are important. AC voltage disturbances can produce commutation failure, particularly at the inverter.
Formula / Key Relationship
LCC reactive demand is a significant fraction of transmitted power and is compensated locally.
Why the Other Options Are Wrong
Option B is incorrect because it includes incorrect statement(s) 2 and omits correct statement(s) 1, 3. Option C is incorrect because it omits correct statement(s) 3. Option D is incorrect because it includes incorrect statement(s) 2.
Exam Shortcut / Approach
Strong AC system and commutation margin matter for LCC.
Common Mistake
LCC cannot normally operate a passive AC network without a voltage source.
Quick Revision
Commutation and AC System Strength is linked with LCC-HVDC, HVDC Transmission and Power Systems. Strong AC system and commutation margin matter for LCC.
More HVDC Transmission questions