Analyzing Delta-Delta System Voltage Relationship

Let's examine the first statement: "In a delta-delta system, the line voltage and phase voltage are equal."

• In a delta ($\Delta$) connection, each line is connected directly across one phase winding of the source or load.
• The voltage across a phase winding is called the phase voltage, denoted as $V_{ph}$.
• The voltage between any two lines is called the line voltage, denoted as $V_L$.
• Because the lines are directly connected to the phase windings in a delta configuration, the line voltage is exactly the same as the phase voltage.
• Therefore, the statement $V_L = V_{ph}$ for a delta-delta system is TRUE.

Evaluating Y-Connected Load Voltage Sequence

Now, let's look at the second statement: "When a Y-connected load is supplied by voltages in abc phase sequence, the line voltages lag the corresponding phase voltages by 30°."

• In a Y (or Wye/Star) connection, phase voltages are measured from the neutral point to each line (e.g., $V_{an}$, $V_{bn}$, $V_{cn}$).
• Line voltages are measured between pairs of lines (e.g., $V_{ab}$, $V_{bc}$, $V_{ca}$).
• The relationship between line voltage ($V_L$) and phase voltage ($V_{ph}$) in a Y-connected system is given by $V_L = \sqrt{3} V_{ph}$.
• Crucially, the line voltage leads the corresponding phase voltage by 30 degrees. For example, the line voltage $V_{ab}$ leads the phase voltage $V_{an}$ by $30^{\circ}$.
• The statement claims that line voltages *lag* the corresponding phase voltages by $30^{\circ}$. This is incorrect; they lead.
• Therefore, the statement is FALSE.

Conclusion

Based on the analysis of both statements:

• Statement 1: TRUE
• Statement 2: FALSE

This corresponds to the option where statement 1 is TRUE and statement 2 is FALSE.