void form_y()                    /* 形成節點導納矩陣 */
 {
  float S;
  int i1,j1;
  {for(i=1;i<=m;i++)   
     if(zhilu[i].bb!=1)  /*變壓器變比不為1時節點導納矩陣的主對角線上的導納*/
        {i1=zhilu[i].p1;
	 j1=zhilu[i].p2;
	  S=zhilu[i].r*zhilu[i].r+zhilu[i].x*zhilu[i].x;
           if(S==0)  continue;
	     G[i1][i1]+=zhilu[i].r/(S*zhilu[i].bb*zhilu[i].bb);
	 B[i1][i1]+=-zhilu[i].x/(S*zhilu[i].bb*zhilu[i].bb);
         G[j1][j1]+=zhilu[i].r/S;
         B[j1][j1]+=-zhilu[i].x/S;
       }           
       else             /*變壓器變比為1時節點導納矩陣的主對角線上的導納*/
      for(j=0;j<=n;j++)
	 if((zhilu[i].p1==j)||(zhilu[i].p2==j))
	   { S=zhilu[i].r*zhilu[i].r+zhilu[i].x*zhilu[i].x;
	 if(S==0)  continue;
	     G[j][j]+=zhilu[i].r/S;
	     B[j][j]+=-zhilu[i].x/S;
	   }
  }


  for(i=1;i<=n;i++)              /*對地導納*/
  if((zhilu[i].p1==0)||(zhilu[i].p2==0))
    {S=zhilu[i].r*zhilu[i].r+zhilu[i].x*zhilu[i].x;
  if(S==0) {G[0][i]=B[0][i]=G[i][0]=B[i][0]=0;continue;}
        G[0][i]+=zhilu[i].r/S;
        B[0][i]+=-zhilu[i].x/S;
        G[i][0]=G[0][i];
        B[i][0]=B[0][i];
    }

  for(k=1;k<=m;k++)              /*節點導納矩陣非主對角線上的導納*/
      { i=zhilu[k].p1;
	j=zhilu[k].p2;
	S=zhilu[k].r*zhilu[k].r+zhilu[k].x*zhilu[k].x;
	if(S==0)  continue;
	G[i][j]+=-zhilu[k].r/S*zhilu[k].bb;
	B[i][j]+=zhilu[k].x/S*zhilu[k].bb;
	G[j][i]=G[i][j];
	B[j][i]=B[i][j];
	}
                         /*輸出節點導納矩陣*/
  fprintf(fp2,"\n\n             ********* 計算結果 *********\n");
  fprintf(fp2,"\n  節點導納矩陣為:");
  for(i=1;i<=n;i++)
     { fprintf(fp2,"\n     ");
       for(j=1;j<=n;j++)
	   fprintf(fp2,"%8.5f+j%8.5f   ",G[i][j],B[i][j]);
  }
    fprintf(fp2,"\n  ==============================================================\n");
   }